mirror of
https://github.com/golang/go
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766f89b5c6
cmd/vet has several precision improvements for the checkers copylock, printf, sortslice, testinggoroutine, and tests. Adds a high level mention in the release notes and an example of string constant concatenation. Updates #47694 Change-Id: I7a342a57ca3fd9e2f3e8ec99f7b647269798317f Reviewed-on: https://go-review.googlesource.com/c/go/+/370734 Reviewed-by: Russ Cox <rsc@golang.org> Reviewed-by: Robert Findley <rfindley@google.com> Trust: Tim King <taking@google.com> Run-TryBot: Tim King <taking@google.com> TryBot-Result: Gopher Robot <gobot@golang.org>
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HTML
<!--{
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"Title": "Go 1.18 Release Notes",
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"Path": "/doc/go1.18"
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}-->
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<!--
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NOTE: In this document and others in this directory, the convention is to
|
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set fixed-width phrases with non-fixed-width spaces, as in
|
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<code>hello</code> <code>world</code>.
|
||
Do not send CLs removing the interior tags from such phrases.
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-->
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<style>
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main ul li { margin: 0.5em 0; }
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</style>
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<h2 id="introduction">DRAFT RELEASE NOTES — Introduction to Go 1.18</h2>
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|
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<p>
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<strong>
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Go 1.18 is not yet released. These are work-in-progress
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release notes. Go 1.18 is expected to be released in February 2022.
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</strong>
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</p>
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<h2 id="language">Changes to the language</h2>
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<h3 id="generics">Generics</h3>
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<p><!-- https://golang.org/issue/43651, https://golang.org/issue/45346 -->
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Go 1.18 includes an implementation of generic features as described by the
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<a href="https://go.googlesource.com/proposal/+/refs/heads/master/design/43651-type-parameters.md">Type
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Parameters Proposal</a>.
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This includes major - but fully backward-compatible - changes to the language.
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The following is a list of the most visible changes. For a more comprehensive overview, see the
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<a href="https://go.googlesource.com/proposal/+/refs/heads/master/design/43651-type-parameters.md">proposal</a>.
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For details see the <a href="https://golang.org/ref/spec">language spec</a>.
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</p>
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<ul>
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<li>
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The syntax for
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<a href="https://golang.org/ref/spec#Function_declarations">Function</a> and
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<a href="https://golang.org/ref/spec#Type_declarations">type declarations</a>
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now accepts
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<a href="https://golang.org/ref/spec#Type_parameters">type parameters</a>.
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</li>
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<li>
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Parameterized functions and types can be instantiated by following them with a list of
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type arguments in square brackets.
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</li>
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<li>
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The new token <code>~</code> has been added to the set of
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<a href="https://golang.org/ref/spec#Operators_and_punctuation">operators and punctuation</a>.
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</li>
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<li>
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The syntax for
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<a href="https://golang.org/ref/spec#Interface_types">Interface types</a>
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now permits the embedding of arbitrary types (not just type names of interfaces)
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as well as union and <code>~T</code> type elements. Such interfaces may only be used
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as type constraints.
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An interface now defines a set of types as well as a set of methods.
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</li>
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<li>
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The new
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<a href="https://golang.org/ref/spec#Predeclared_identifiers">predeclared identifier</a>
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<code>any</code> is an alias for the empty interface. It may be used instead of
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<code>interface{}</code>.
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</li>
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<li>
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The new
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<a href="https://golang.org/ref/spec#Predeclared_identifiers">predeclared identifier</a>
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<code>comparable</code> is an interface the denotes the set of all types which can be
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compared using <code>==</code> or <code>!=</code>. It may only be used as (or embedded in)
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a type constraint.
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</li>
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</ul>
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<p>
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The current generics implementation has the following limitations:
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<ul>
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<li><!-- https://golang.org/issue/47631 -->
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The Go compiler cannot currently handle type declarations inside generic functions
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or methods. We hope to provide support for this feature in Go 1.19.
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</li>
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</ul>
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</p>
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<h3 id="bug_fixes">Bug fixes</h3>
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<p>
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The Go 1.18 compiler now correctly reports <code>declared but not used</code> errors
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for variables that are set inside a function literal but are never used. Before Go 1.18,
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the compiler did not report an error in such cases. This fixes long-outstanding compiler
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issue <a href="https://golang.org/issue/8560">#8560</a>. As a result of this change,
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(possibly incorrect) programs may not compile anymore. The necessary fix is
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straightforward: fix the program if it was in fact incorrect, or use the offending
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variable, for instance by assigning it to the blank identifier <code>_</code>.
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Since <code>go vet</code> always pointed out this error, the number of affected
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programs is likely very small.
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</p>
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<p>
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The Go 1.18 compiler now reports an overflow when passing a rune constant expression
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such as <code>'1' << 32</code> as an argument to the predeclared functions
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<code>print</code> and <code>println</code>, consistent with the behavior of
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user-defined functions. Before Go 1.18, the compiler did not report an error
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in such cases but silently accepted such constant arguments if they fit into an
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<code>int64</code>. As a result of this change, (possibly incorrect) programs
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may not compile anymore. The necessary fix is straightforward: fix the program if it
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was in fact incorrect, or explicitly convert the offending argument to the correct type.
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Since <code>go vet</code> always pointed out this error, the number of affected
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programs is likely very small.
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</p>
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<h2 id="ports">Ports</h2>
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<h3 id="amd64">AMD64</h3>
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<p><!-- CL 349595 -->
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Go 1.18 introduces the new <code>GOAMD64</code> environment variable which selects
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a version of the AMD64 architecture. Allowed values are <code>v1</code>,
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<code>v2</code>, <code>v3</code>, or <code>v4</code>. Each higher level requires,
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and takes advantage of, additional processor features. A detailed description of the
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versions is <a href="https://en.wikipedia.org/wiki/X86-64#Microarchitecture_levels">here</a>.
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</p>
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<p>
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The <code>GOAMD64</code> environment variable defaults to <code>v1</code>.
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</p>
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|
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<h3 id="riscv">RISC-V</h3>
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||
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<p><!-- golang.org/issue/47100, CL 334872 -->
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The 64-bit RISC-V architecture on Linux (the <code>linux/riscv64</code> port)
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now supports the <code>c-archive</code> and <code>c-shared</code> build modes.
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</p>
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<h3 id="windows">Windows</h3>
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<p><!-- https://golang.org/issue/49759 -->
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The <code>windows/arm</code> and <code>windows/arm64</code> ports now support
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non-cooperative preemption, bringing that capability to all four Windows
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ports, which should hopefully address subtle bugs encountered when calling
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into Win32 functions that block for extended periods of time.
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</p>
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<h3 id="ios">iOS</h3>
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<p><!-- golang.org/issue/48076, golang.org/issue/49616 -->
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On iOS (the <code>ios/arm64</code> port)
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and iOS simulator running on AMD64-based macOS (the <code>ios/amd64</code> port),
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Go 1.18 now requires iOS 12 or later; support for previous versions has been discontinued.
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</p>
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<h3 id="freebsd">FreeBSD</h3>
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<p>
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Go 1.18 is the last release that is supported on FreeBSD 11.x, which has
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already reached end-of-life. Go 1.19 will require FreeBSD 12.2+ or FreeBSD
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13.0+.
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FreeBSD 13.0+ will require a kernel with the COMPAT_FREEBSD12 option set (this is the default).
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</p>
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<h2 id="tools">Tools</h2>
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<h3 id="fuzzing">Fuzzing</h3>
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<p>
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Go 1.18 includes an implementation of fuzzing as described by
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<a href="https://golang.org/issue/44551">the fuzzing proposal</a>.
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</p>
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<p>
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See the <a href="https://go.dev/doc/fuzz">fuzzing landing page</a> to get
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started.
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</p>
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<p>
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Please be aware that fuzzing can consume a lot of memory and may impact your
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machine’s performance while it runs. Also be aware that the fuzzing engine
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writes values that expand test coverage to a fuzz cache directory within
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<code>$GOCACHE/fuzz</code> while it runs. There is currently no limit to the
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number of files or total bytes that may be written to the fuzz cache, so it
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may occupy a large amount of storage (possibly several GBs).
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</p>
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<h3 id="go-command">Go command</h3>
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<p><!-- golang.org/issue/43684 -->
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<code>go</code> <code>get</code> no longer builds or installs packages in
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module-aware mode. <code>go</code> <code>get</code> is now dedicated to
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adjusting dependencies in <code>go.mod</code>. Effectively, the
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<code>-d</code> flag is always enabled. To install the latest version
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of an executable outside the context of the current module, use
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<a href="https://golang.org/ref/mod#go-install"><code>go</code>
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<code>install</code> <code>example.com/cmd@latest</code></a>. Any
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<a href="https://golang.org/ref/mod#version-queries">version query</a>
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may be used instead of <code>latest</code>. This form of <code>go</code>
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<code>install</code> was added in Go 1.16, so projects supporting older
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versions may need to provide install instructions for both <code>go</code>
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<code>install</code> and <code>go</code> <code>get</code>. <code>go</code>
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<code>get</code> now reports an error when used outside a module, since there
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is no <code>go.mod</code> file to update. In GOPATH mode (with
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<code>GO111MODULE=off</code>), <code>go</code> <code>get</code> still builds
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and installs packages, as before.
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</p>
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<p><!-- golang.org/issue/37475 -->
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The <code>go</code> command now embeds version control information in
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binaries including the currently checked-out revision, commit time, and a
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flag indicating whether edited or untracked files are present. Version
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control information is embedded if the <code>go</code> command is invoked in
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a directory within a Git, Mercurial, Fossil, or Bazaar repository, and the
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<code>main</code> package and its containing main module are in the same
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repository. This information may be omitted using the flag
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<code>-buildvcs=false</code>.
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</p>
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<p><!-- golang.org/issue/37475 -->
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Additionally, the <code>go</code> command embeds information about the build
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including build and tool tags (set with <code>-tags</code>), compiler,
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assembler, and linker flags (like <code>-gcflags</code>), whether cgo was
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enabled, and if it was, the values of the cgo environment variables
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(like <code>CGO_CFLAGS</code>). This information may be omitted using the
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flag <code>-buildinfo=false</code>. Both VCS and build information may be
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read together with module information using <code>go</code>
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<code>version</code> <code>-m</code> <code>file</code> or
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<code>runtime/debug.ReadBuildInfo</code> (for the currently running binary)
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or the new <a href="#debug/buildinfo"><code>debug/buildinfo</code></a>
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package.
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</p>
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<p><!-- https://golang.org/issue/44435 -->
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If the main module's <code>go.mod</code> file
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specifies <a href="/ref/mod#go-mod-file-go"><code>go</code> <code>1.17</code></a>
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or higher, <code>go</code> <code>mod</code> <code>download</code> without
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arguments now downloads source code for only the modules
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explicitly <a href="/ref/mod#go-mod-file-require">required</a> in the main
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module's <code>go.mod</code> file. (In a <code>go</code> <code>1.17</code> or
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higher module, that set already includes all dependencies needed to build the
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packages and tests in the main module.)
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To also download source code for transitive dependencies, use
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<code>go</code> <code>mod</code> <code>download</code> <code>all</code>.
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</p>
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|
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<p><!-- https://golang.org/issue/47327 -->
|
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The <code>go</code> <code>mod</code> <code>vendor</code> subcommand now
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supports a <code>-o</code> flag to set the output directory.
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(Other <code>go</code> commands still read from the <code>vendor</code>
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directory at the module root when loading packages
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with <code>-mod=vendor</code>, so the main use for this flag is for
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third-party tools that need to collect package source code.)
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</p>
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<p><!-- CL 298612 -->
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The <code>go</code> <code>build</code> command and related commands
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now support an <code>-asan</code> flag that enables interoperation
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with C (or C++) code compiled with the address sanitizer (C compiler
|
||
option <code>-fsanitize=address</code>).
|
||
</p>
|
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|
||
<h3 id="gofmt"><code>gofmt</code></h3>
|
||
|
||
<p><!-- https://golang.org/issue/43566 -->
|
||
<code>gofmt</code> now reads and formats input files concurrently, with a
|
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memory limit proportional to <code>GOMAXPROCS</code>. On a machine with
|
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multiple CPUs, <code>gofmt</code> should now be significantly faster.
|
||
</p>
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<h3 id="vet"><code>vet</code></h3>
|
||
|
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<h4 id="vet-generics">Updates for Generics</h4>
|
||
|
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<p><!-- https://golang.org/issue/48704 -->
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The <code>vet</code> tool is updated to support generic code. In most cases,
|
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it reports an error in generic code whenever it would report an error in the
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equivalent non-generic code after substituting for type parameters with a
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type from their
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<a href="https://golang.org/ref/spec#Interface_types">type set</a>.
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For example, <code>vet</code> reports a format error in
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<pre>func Print[T ~int|~string](t T) {
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fmt.Printf("%d", t)
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}</pre>
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because it would report a format error in the non-generic equivalent of
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<code>Print[string]</code>:
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<pre>func PrintString(x string) {
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fmt.Printf("%d", x)
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}</pre>
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</p>
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<h4 id="vet-precision">Precision improvements for existing checkers</h4>
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<p><!-- CL 323589 356830 319689 355730 351553 338529 -->
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The <code>cmd/vet</code> checkers <code>copylock</code>, <code>printf</code>,
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<code>sortslice</code>, <code>testinggoroutine</code>, and <code>tests</code>
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||
have all had moderate precision improvements to handle additional code patterns.
|
||
This may lead to newly reported errors in existing packages. For example, the
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<code>printf</code> checker now tracks formatting strings created by
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concatenating string constants. So <code>vet</code> will report an error in:
|
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<pre>
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// fmt.Printf formatting directive %d is being passed to Println.
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fmt.Println("%d"+` ≡ x (mod 2)`+"\n", x%2)
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</pre>
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||
</p>
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<h2 id="runtime">Runtime</h2>
|
||
|
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<p><!-- https://golang.org/issue/44167 -->
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The garbage collector now includes non-heap sources of garbage collector work
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(e.g., stack scanning) when determining how frequently to run. As a result,
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garbage collector overhead is more predictable when these sources are
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significant. For most applications these changes will be negligible; however,
|
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some Go applications may now use less memory and spend more time on garbage
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collection, or vice versa, than before. The intended workaround is to tweak
|
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<code>GOGC</code> where necessary.
|
||
</p>
|
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|
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<p><!-- CL 358675, CL 353975, CL 353974 -->
|
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The runtime now returns memory to the operating system more efficiently and has
|
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been tuned to work more aggressively as a result.
|
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</p>
|
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|
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<p><!-- CL 352057, https://golang.org/issue/45728 -->
|
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Go 1.17 generally improved the formatting of arguments in stack traces,
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but could print inaccurate values for arguments passed in registers.
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This is improved in Go 1.18 by printing a question mark (<code>?</code>)
|
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after each value that may be inaccurate.
|
||
</p>
|
||
|
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<h2 id="compiler">Compiler</h2>
|
||
|
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<p><!-- https://golang.org/issue/40724 -->
|
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Go 1.17 <a href="go1.17#compiler">implemented</a> a new way of passing
|
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function arguments and results using registers instead of the stack
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on 64-bit x86 architecture on selected operating systems.
|
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Go 1.18 expands the supported platforms to include 64-bit ARM (<code>GOARCH=arm64</code>),
|
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big- and little-endian 64-bit PowerPC (<code>GOARCH=ppc64</code>, <code>ppc64le</code>),
|
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as well as 64-bit x86 architecture (<code>GOARCH=amd64</code>)
|
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on all operating systems.
|
||
On 64-bit ARM and 64-bit PowerPC systems, benchmarking shows
|
||
typical performance improvements of 10% or more.
|
||
</p>
|
||
|
||
<p>
|
||
As <a href="go1.17#compiler">mentioned</a> in the Go 1.17 release notes,
|
||
this change does not affect the functionality of any safe Go code and
|
||
is designed to have no impact on most assembly code. See the
|
||
<a href="go1.17#compiler">Go 1.17 release notes</a> for more details.
|
||
</p>
|
||
|
||
<p><!-- CL 355497, CL 356869 -->
|
||
The compiler now can inline functions that contain range loops or
|
||
labeled for loops.
|
||
</p>
|
||
|
||
<p><!-- CL 298611 -->
|
||
The new compiler <code>-asan</code> option supports the
|
||
new <code>go</code> command <code>-asan</code> option.
|
||
</p>
|
||
|
||
<p> <!-- https://github.com/golang/go/issues/49569 -->
|
||
Because of changes in the compiler related to supporting generics, the
|
||
Go 1.18 compile speed can be roughly 15% slower than the Go 1.17 compile speed.
|
||
The execution time of the compiled code is not affected. We
|
||
intend to improve the speed of the compiler in Go 1.19.
|
||
</p>
|
||
|
||
<h2 id="linker">Linker</h2>
|
||
|
||
<p><!-- CL 298610 -->
|
||
The new linker <code>-asan</code> option supports the
|
||
new <code>go</code> command <code>-asan</code> option.
|
||
</p>
|
||
|
||
<h2 id="library">Core library</h2>
|
||
|
||
<h3 id="constraints">New <code>constraints</code> package</h3>
|
||
|
||
<p><!-- CL 349709 -->
|
||
The new <a href="/pkg/constraints/"><code>constraints</code></a> package
|
||
defines a set of useful constraints that can be used with type parameters of
|
||
generic functions.
|
||
</p>
|
||
|
||
<h3 id="netip">New <code>net/netip</code> package</h3>
|
||
|
||
<p>
|
||
The new <a href="/pkg/net/netip/"><code>net/netip</code></a>
|
||
package defines a new IP address type, <a href="/pkg/net/netip/#Addr"><code>Addr</code></a>.
|
||
Compared to the existing
|
||
<a href="/pkg/net/#IP"><code>net.IP</code></a> type, the <code>netip.Addr</code> type takes less
|
||
memory, is immutable, and is comparable so it supports <code>==</code>
|
||
and can be used as a map key.
|
||
</p>
|
||
<p>
|
||
In addition to <code>Addr</code>, the package defines
|
||
<a href="/pkg/net/netip/#AddrPort"><code>AddrPort</code></a>, representing
|
||
an IP and port, and
|
||
<a href="/pkg/net/netip/#Prefix"><code>Prefix</code></a>, representing
|
||
a network CIDR prefix.
|
||
</p>
|
||
<p>
|
||
The <a href="/pkg/net/"><code>net</code></a> package includes new
|
||
methods that parallel existing methods, but
|
||
return <code>netip.AddrPort</code> instead of the
|
||
heavier-weight <a href="/pkg/net/#IP"><code>net.IP</code></a> or
|
||
<a href="/pkg/net/#UDPAddr"<code>*net.UDPAddr</code></a> types.
|
||
The <code>net</code> package also now includes functions and methods
|
||
to convert between the existing
|
||
<a href="/pkg/net/#TCPAddr"><code>TCPAddr</code>/<a href="/pkg/net/#UDPAddr"><code>UDPAddr</code>
|
||
types and <code>netip.AddrPort</code>.
|
||
</p>
|
||
|
||
<h3>TODO</h3>
|
||
|
||
<p>
|
||
TODO: complete this section
|
||
</p>
|
||
|
||
<h3 id="minor_library_changes">Minor changes to the library</h3>
|
||
|
||
<p>
|
||
As always, there are various minor changes and updates to the library,
|
||
made with the Go 1 <a href="/doc/go1compat">promise of compatibility</a>
|
||
in mind.
|
||
</p>
|
||
|
||
<p>
|
||
TODO: complete this section
|
||
</p>
|
||
|
||
<dl id="bufio"><dt><a href="/pkg/bufio/">bufio</a></dt>
|
||
<dd>
|
||
<p><!-- CL 345569 -->
|
||
The new <a href="/pkg/bufio#Writer.AvailableBuffer"><code>Writer.AvailableBuffer</code></a>
|
||
method returns an empty buffer with a possibly non-empty capacity for use
|
||
with append-like APIs. After appending, the buffer can be provided to a
|
||
succeeding <code>Write</code> call and possibly avoid any copying.
|
||
</p>
|
||
|
||
<p><!-- CL 345570 -->
|
||
The methods <a href="/pkg/bufio#Reader.Reset"><code>Reader.Reset</code></a> and
|
||
<a href="/pkg/bufio#Writer.Reset"><code>Writer.Reset</code></a>
|
||
now use the default buffer size when called on objects with a
|
||
<code>nil</code> buffer.
|
||
</p>
|
||
</dd>
|
||
</dl><!-- bufio -->
|
||
|
||
<dl id="bytes"><dt><a href="/pkg/bytes/">bytes</a></dt>
|
||
<dd>
|
||
<p><!-- CL 351710 -->
|
||
The new <a href="/pkg/bytes/#Cut"><code>Cut</code></a> function
|
||
slices a <code>[]byte</code> around a separator. It can replace
|
||
and simplify many common uses of
|
||
<a href="/pkg/bytes/#Index"><code>Index</code></a>,
|
||
<a href="/pkg/bytes/#IndexByte"><code>IndexByte</code></a>,
|
||
<a href="/pkg/bytes/#IndexRune"><code>IndexRune</code></a>,
|
||
and <a href="/pkg/bytes/#SplitN"><code>SplitN</code></a>.
|
||
</p>
|
||
|
||
<p><!-- CL 323318, CL 332771 -->
|
||
<a href="/pkg/bytes/#Trim"><code>Trim</code></a>, <a href="/pkg/bytes/#TrimLeft"><code>TrimLeft</code></a>,
|
||
and <a href="/pkg/bytes/#TrimRight"><code>TrimRight</code></a> are now allocation free and, especially for
|
||
small ASCII cutsets, up to 10 times faster.
|
||
</p>
|
||
|
||
<p><!-- CL 359485 -->
|
||
The <a href="/pkg/bytes/#Title"><code>Title</code></a> function is now deprecated. It doesn't
|
||
handle Unicode punctuation and language-specific capitalization rules, and is superseded by the
|
||
<a href="https://golang.org/x/text/cases">golang.org/x/text/cases</a> package.
|
||
</p>
|
||
</dd>
|
||
</dl><!-- bytes -->
|
||
|
||
<dl id="crypto/tls"><dt><a href="/pkg/crypto/tls/">crypto/tls</a></dt>
|
||
<dd>
|
||
<p><!-- CL 325250 -->
|
||
The new <a href="/pkg/crypto/tls/#Conn.NetConn"><code>Conn.NetConn</code></a>
|
||
method allows access to the underlying
|
||
<a href="/pkg/net#Conn"><code>net.Conn</code></a>.
|
||
</p>
|
||
</dd>
|
||
</dl><!-- crypto/tls -->
|
||
|
||
<dl id="debug/buildinfo"><dt><a href="/pkg/debug/buildinfo">debug/buildinfo</a></dt>
|
||
<dd>
|
||
<p><!-- golang.org/issue/39301 -->
|
||
This new package provides access to module versions, version control
|
||
information, and build flags embedded in executable files built by
|
||
the <code>go</code> command. The same information is also available via
|
||
<a href="/pkg/runtime/debug#ReadBuildInfo"><code>runtime/debug.ReadBuildInfo</code></a>
|
||
for the currently running binary and via <code>go</code>
|
||
<code>version</code> <code>-m</code> on the command line.
|
||
</p>
|
||
</dd>
|
||
</dl>
|
||
|
||
<dl id="go/ast"><dt><a href="/pkg/go/ast/">go/ast</a></dt>
|
||
<dd>
|
||
<p><!-- https://golang.org/issue/47781, CL 325689, CL 327149, CL 348375, CL 348609 -->
|
||
Per the proposal
|
||
<a href="https://go.googlesource.com/proposal/+/master/design/47781-parameterized-go-ast.md">
|
||
Additions to go/ast and go/token to support parameterized functions and types
|
||
</a>
|
||
the following additions are made to the <a href="/pkg/go/ast"><code>go/ast</code></a> package:
|
||
<ul>
|
||
<li>
|
||
the <a href="/pkg/go/ast/#FuncType"><code>FuncType</code></a>
|
||
and <a href="/pkg/go/ast/#TypeSpec"><code>TypeSpec</code></a>
|
||
nodes have a new field <code>TypeParams</code> to hold type parameters, if any.
|
||
</li>
|
||
<li>
|
||
The new expression node <a href="/pkg/go/ast/#IndexListExpr"><code>IndexListExpr</code></a>
|
||
represents index expressions with multiple indices, used for function and type instantiations
|
||
with more than one explicit type argument.
|
||
</li>
|
||
</ul>
|
||
</p>
|
||
</dd>
|
||
</dl>
|
||
|
||
<dl id="go/constant"><dt><a href="/pkg/go/constant/">go/constant</a></dt>
|
||
<dd>
|
||
<p><!-- https://golang.org/issue/46211, CL 320491 -->
|
||
The new <a href="/pkg/go/constant/#Kind.String"><code>Kind.String</code></a>
|
||
method returns a human-readable name for the receiver kind.
|
||
</p>
|
||
</dd>
|
||
</dl>
|
||
|
||
<dl id="go/token"><dt><a href="/pkg/go/token/">go/token</a></dt>
|
||
<dd>
|
||
<p><!-- https://golang.org/issue/47781, CL 324992 -->
|
||
The new constant <a href="/pkg/go/token/#TILDE"><code>TILDE</code></a>
|
||
represents the <code>~</code> token per the proposal
|
||
<a href="https://go.googlesource.com/proposal/+/master/design/47781-parameterized-go-ast.md">
|
||
Additions to go/ast and go/token to support parameterized functions and types
|
||
</a>.
|
||
</p>
|
||
</dd>
|
||
</dl>
|
||
|
||
<dl id="go/types"><dt><a href="/pkg/go/types/">go/types</a></dt>
|
||
<dd>
|
||
<p><!-- https://golang.org/issue/46648 -->
|
||
The new <a href="/pkg/go/types/#Config.GoVersion"><code>Config.GoVersion</code></a>
|
||
field sets the accepted Go language version.
|
||
</p>
|
||
|
||
<p><!-- https://golang.org/issue/47916 -->
|
||
Per the proposal
|
||
<a href="https://go.googlesource.com/proposal/+/master/design/47916-parameterized-go-types.md">
|
||
Additions to go/types to support type parameters
|
||
</a>
|
||
the following additions are made to the <a href="/pkg/go/types"><code>go/types</code></a> package:
|
||
</p>
|
||
<ul>
|
||
<li>
|
||
The new type
|
||
<a href="/pkg/go/types/#TypeParam"><code>TypeParam</code></a>, factory function
|
||
<a href="/pkg/go/types/#NewTypeParam"><code>NewTypeParam</code></a>,
|
||
and associated methods are added to represent a type parameter.
|
||
</li>
|
||
<li>
|
||
The new type
|
||
<a href="/pkg/go/types/#TypeParamList"><code>TypeParamList</code></a> holds a list of
|
||
type parameters.
|
||
</li>
|
||
<li>
|
||
The new type
|
||
<a href="/pkg/go/types/#TypeList"><code>TypeList</code></a> holds a list of types.
|
||
</li>
|
||
<li>
|
||
The new factory function
|
||
<a href="/pkg/go/types/#NewSignatureType"><code>NewSignatureType</code></a> allocates a
|
||
<a href="/pkg/go/types/#Signature"><code>Signature</code></a> with
|
||
(receiver or function) type parameters.
|
||
To access those type parameters, the <code>Signature</code> type has two new methods
|
||
<a href="/pkg/go/types/#Signature.RecvTypeParams"><code>Signature.RecvTypeParams</code></a> and
|
||
<a href="/pkg/go/types/#Signature.TypeParams"><code>Signature.TypeParams</code></a>.
|
||
</li>
|
||
<li>
|
||
<a href="/pkg/go/types/#Named"><code>Named</code></a> types have four new methods:
|
||
<a href="/pkg/go/types/#Named.Origin"><code>Named.Origin</code></a> to get the original
|
||
parameterized types of instantiated types,
|
||
<a href="/pkg/go/types/#Named.TypeArgs"><code>Named.TypeArgs</code></a> and
|
||
<a href="/pkg/go/types/#Named.TypeParams"><code>Named.TypeParams</code></a> to get the
|
||
type arguments or type parameters of an instantiated or parameterized type, and
|
||
<a href="/pkg/go/types/#Named.TypeParams"><code>Named.SetTypeParams</code></a> to set the
|
||
type parameters (for instance, when importing a named type where allocation of the named
|
||
type and setting of type parameters cannot be done simultaneously due to possible cycles).
|
||
</li>
|
||
<li>
|
||
The <a href="/pkg/go/types/#Interface"><code>Interface</code></a> type has four new methods:
|
||
<a href="/pkg/go/types/#Interface.IsComparable"><code>Interface.IsComparable</code></a> and
|
||
<a href="/pkg/go/types/#Interface.IsMethodSet"><code>Interface.IsMethodSet</code></a> to
|
||
query properties of the type set defined by the interface, and
|
||
<a href="/pkg/go/types/#Interface.MarkImplicit"><code>Interface.MarkImplicit</code></a> and
|
||
<a href="/pkg/go/types/#Interface.IsImplicit"><code>Interface.IsImplicit</code></a> to set
|
||
and test whether the interface is an implicit interface around a type constraint literal.
|
||
</li>
|
||
<li>
|
||
The new types
|
||
<a href="/pkg/go/types/#Union"><code>Union</code></a> and
|
||
<a href="/pkg/go/types/#Term"><code>Term</code></a>, factory functions
|
||
<a href="/pkg/go/types/#NewUnion"><code>NewUnion</code></a> and
|
||
<a href="/pkg/go/types/#NewTerm"><code>NewTerm</code></a>, and associated
|
||
methods are added to represent type sets in interfaces.
|
||
</li>
|
||
<li>
|
||
The new function
|
||
<a href="/pkg/go/types/#Instantiate"><code>Instantiate</code></a>
|
||
instantiates a parameterized type.
|
||
</li>
|
||
<li>
|
||
The new <a href="/pkg/go/types/#Info.Instances"><code>Info.Instances</code></a>
|
||
map records function and type instantiations through the new
|
||
<a href="/pkg/go/types/#Instance"><code>Instance</code></a> type.
|
||
</li>
|
||
<li><!-- CL 342671 -->
|
||
The new type <a href="/pkg/go/types/#ArgumentError"><code>ArgumentError</code></a>
|
||
and associated methods are added to represent an error related to a type argument.
|
||
</li>
|
||
<li><!-- CL 353089 -->
|
||
The new type <a href="/pkg/go/types/#Context"><code>Context</code></a> and factory function
|
||
<a href="/pkg/go/types/#NewContext"><code>NewContext</code></a>
|
||
are added to facilitate sharing of identical type instances across type-checked packages.
|
||
</li>
|
||
</ul>
|
||
</dd>
|
||
</dl>
|
||
|
||
<dl id="image/draw"><dt><a href="/pkg/image/draw/">image/draw</a></dt>
|
||
<dd>
|
||
<p><!-- CL 340049 -->
|
||
The <code>Draw</code> and <code>DrawMask</code> fallback implementations
|
||
(used when the arguments are not the most common image types) are now
|
||
faster when those arguments implement the optional
|
||
<a href="/pkg/image/draw/#RGBA64Image"><code>draw.RGBA64Image</code></a>
|
||
and <a href="/pkg/image/#RGBA64Image"><code>image.RGBA64Image</code></a>
|
||
interfaces that were added in Go 1.17.
|
||
</p>
|
||
</dd>
|
||
</dl><!-- image/draw -->
|
||
|
||
<dl id="net"><dt><a href="/pkg/net/">net</a></dt>
|
||
<dd>
|
||
<p><!-- CL 340261 -->
|
||
<a href="/pkg/net#Error"><code>net.Error.Temporary</code></a> has been deprecated.
|
||
</p>
|
||
</dd>
|
||
</dl><!-- net -->
|
||
|
||
<dl id="net/http"><dt><a href="/pkg/net/http/">net/http</a></dt>
|
||
<dd>
|
||
<p><!-- CL 330852 -->
|
||
On WebAssembly targets, the <code>Dial</code>, <code>DialContext</code>,
|
||
<code>DialTLS</code> and <code>DialTLSContext</code> method fields in
|
||
<a href="/pkg/net/http/#Transport"><code>Transport</code></a>
|
||
will now be correctly used, if specified, for making HTTP requests.
|
||
</p>
|
||
|
||
<p><!-- CL 338590 -->
|
||
The new
|
||
<a href="/pkg/net/http#Cookie.Valid"><code>Cookie.Valid</code></a>
|
||
method reports whether the cookie is valid.
|
||
</p>
|
||
</dd>
|
||
</dl><!-- net/http -->
|
||
|
||
<dl id="os/user"><dt><a href="/pkg/os/user/">os/user</a></dt>
|
||
<dd>
|
||
<p><!-- CL 330753 -->
|
||
<a href="/pkg/os/user#User.GroupIds"><code>User.GroupIds</code></a>.
|
||
now uses a Go native implementation when cgo is not available.
|
||
</p>
|
||
</dd>
|
||
</dl><!-- os/user -->
|
||
|
||
<dl id="reflect"><dt><a href="/pkg/reflect/">reflect</a></dt>
|
||
<dd>
|
||
<p><!-- CL 356049, CL 320929 -->
|
||
The new
|
||
<a href="/pkg/reflect/#Value.SetIterKey"><code>Value.SetIterKey</code></a>
|
||
and <a href="/pkg/reflect/#Value.SetIterValue"><code>Value.SetIterValue</code></a>
|
||
methods set a Value using a map iterator as the source. They are equivalent to
|
||
<code>Value.Set(iter.Key())</code> and <code>Value.Set(iter.Value())</code> but
|
||
do fewer allocations.
|
||
</p>
|
||
|
||
<p><!-- CL 350691 -->
|
||
The new
|
||
<a href="/pkg/reflect/#Value.UnsafePointer"><code>Value.UnsafePointer</code></a>
|
||
method returns the Value's value as an <a href="/pkg/unsafe/#Pointer"><code>unsafe.Pointer</code></a>.
|
||
This allows callers to migrate from <a href="/pkg/reflect/#Value.UnsafeAddr"><code>Value.UnsafeAddr</code></a>
|
||
and <a href="/pkg/reflect/#Value.Pointer"><code>Value.Pointer</code></a>
|
||
to eliminate the need to perform uintptr to unsafe.Pointer conversions at the callsite (as unsafe.Pointer rules require).
|
||
</p>
|
||
|
||
<p><!-- CL 321891 -->
|
||
The new
|
||
<a href="/pkg/reflect/#MapIter.Reset"><code>MapIter.Reset</code></a>
|
||
method changes its receiver to iterate over a
|
||
different map. The use of
|
||
<a href="/pkg/reflect/#MapIter.Reset"><code>MapIter.Reset</code></a>
|
||
allows allocation-free iteration
|
||
over many maps.
|
||
</p>
|
||
|
||
<p><!-- CL 352131 -->
|
||
A number of methods (
|
||
<a href="/pkg/reflect#Value.CanInt"><code>Value.CanInt</code></a>,
|
||
<a href="/pkg/reflect#Value.CanUint"><code>Value.CanUint</code></a>,
|
||
<a href="/pkg/reflect#Value.CanFloat"><code>Value.CanFloat</code></a>,
|
||
<a href="/pkg/reflect#Value.CanComplex"><code>Value.CanComplex</code></a>
|
||
)
|
||
have been added to
|
||
<a href="/pkg/reflect#Value"><code>Value</code></a>
|
||
to test if a conversion is safe.
|
||
</p>
|
||
|
||
<p><!-- CL 357962 -->
|
||
<a href="/pkg/reflect#Value.FieldByIndexErr"><code>Value.FieldByIndexErr</code></a>
|
||
has been added to avoid the panic that occurs in
|
||
<a href="/pkg/reflect#Value.FieldByIndex"><code>Value.FieldByIndex</code></a>
|
||
when stepping through a nil pointer to an embedded struct.
|
||
</p>
|
||
|
||
<p><!-- CL 341333 -->
|
||
<a href="/pkg/reflect#Ptr"><code>reflect.Ptr</code></a> and
|
||
<a href="/pkg/reflect#PtrTo"><code>reflect.PtrTo</code></a>
|
||
have been renamed to
|
||
<a href="/pkg/reflect#Pointer"><code>reflect.Pointer</code></a> and
|
||
<a href="/pkg/reflect#PointerTo"><code>reflect.PointerTo</code></a>,
|
||
respectively, for consistency with the rest of the reflect package.
|
||
The old names will continue to work, but will be deprecated in a
|
||
future Go release.
|
||
</p>
|
||
</dd>
|
||
</dl><!-- reflect -->
|
||
|
||
<dl id="regexp"><dt><a href="/pkg/regexp/">regexp</a></dt>
|
||
<dd>
|
||
<p><!-- CL 354569 -->
|
||
<a href="/pkg/regexp/"><code>regexp</code></a>
|
||
now treats each invalid byte of a UTF-8 string as <code>U+FFFD</code>.
|
||
</p>
|
||
</dd>
|
||
</dl><!-- regexp -->
|
||
|
||
<dl id="strconv"><dt><a href="/pkg/strconv/">strconv</a></dt>
|
||
<dd>
|
||
<p><!-- CL 343877 -->
|
||
<a href="/pkg/strconv/#strconv.Unquote"><code>strconv.Unquote</code></a>
|
||
now rejects Unicode surrogate halves.
|
||
</p>
|
||
</dd>
|
||
</dl><!-- strconv -->
|
||
|
||
<dl id="strings"><dt><a href="/pkg/strings/">strings</a></dt>
|
||
<dd>
|
||
<p><!-- CL 351710 -->
|
||
The new <a href="/pkg/strings/#Cut"><code>Cut</code></a> function
|
||
slices a <code>string</code> around a separator. It can replace
|
||
and simplify many common uses of
|
||
<a href="/pkg/strings/#Index"><code>Index</code></a>,
|
||
<a href="/pkg/strings/#IndexByte"><code>IndexByte</code></a>,
|
||
<a href="/pkg/strings/#IndexRune"><code>IndexRune</code></a>,
|
||
and <a href="/pkg/strings/#SplitN"><code>SplitN</code></a>.
|
||
</p>
|
||
|
||
<p><!-- CL 345849 -->
|
||
The new <a href="/pkg/strings/#Clone"><code>Clone</code></a> function copies the input
|
||
<code>string</code> without the returned cloned <code>string</code> referencing
|
||
the input string's memory.
|
||
</p>
|
||
|
||
<p><!-- CL 323318, CL 332771 -->
|
||
<a href="/pkg/strings/#Trim"><code>Trim</code></a>, <a href="/pkg/strings/#TrimLeft"><code>TrimLeft</code></a>,
|
||
and <a href="/pkg/strings/#TrimRight"><code>TrimRight</code></a> are now allocation free and, especially for
|
||
small ASCII cutsets, up to 10 times faster.
|
||
</p>
|
||
|
||
<p><!-- CL 359485 -->
|
||
The <a href="/pkg/strings/#Title"><code>Title</code></a> function is now deprecated. It doesn't
|
||
handle Unicode punctuation and language-specific capitalization rules, and is superseded by the
|
||
<a href="https://golang.org/x/text/cases">golang.org/x/text/cases</a> package.
|
||
</p>
|
||
</dd>
|
||
</dl><!-- strings -->
|
||
|
||
<dl id="sync"><dt><a href="/pkg/sync/">sync</a></dt>
|
||
<dd>
|
||
<p><!-- CL 319769 -->
|
||
The new methods
|
||
<a href="/pkg/sync#Mutex.TryLock"><code>Mutex.TryLock</code></a>,
|
||
<a href="/pkg/sync#RWMutex.TryLock"><code>RWMutex.TryLock</code></a>, and
|
||
<a href="/pkg/sync#RWMutex.TryRLock"><code>RWMutex.TryRLock</code></a>,
|
||
will acquire the lock if it is not currently held.
|
||
</p>
|
||
</dd>
|
||
</dl><!-- sync -->
|
||
|
||
<dl id="syscall"><dt><a href="/pkg/syscall/">syscall</a></dt>
|
||
<dd>
|
||
<p><!-- CL 336550 -->
|
||
The new function <a href="/pkg/syscall/?GOOS=windows#SyscallN"><code>SyscallN</code></a>
|
||
has been introduced for Windows, allowing for calls with arbitrary number
|
||
of arguments. As a result,
|
||
<a href="/pkg/syscall/?GOOS=windows#Syscall"><code>Syscall</code></a>,
|
||
<a href="/pkg/syscall/?GOOS=windows#Syscall6"><code>Syscall6</code></a>,
|
||
<a href="/pkg/syscall/?GOOS=windows#Syscall9"><code>Syscall9</code></a>,
|
||
<a href="/pkg/syscall/?GOOS=windows#Syscall12"><code>Syscall12</code></a>,
|
||
<a href="/pkg/syscall/?GOOS=windows#Syscall15"><code>Syscall15</code></a>, and
|
||
<a href="/pkg/syscall/?GOOS=windows#Syscall18"><code>Syscall18</code></a> are
|
||
deprecated in favor of <a href="/pkg/syscall/?GOOS=windows#SyscallN"><code>SyscallN</code></a>.
|
||
</p>
|
||
|
||
<p><!-- CL 355570 -->
|
||
<a href="/pkg/syscall/?GOOS=freebsd#SysProcAttr.Pdeathsig"><code>SysProcAttr.Pdeathsig</code></a>.
|
||
is now supported in FreeBSD.
|
||
</p>
|
||
</dd>
|
||
</dl><!-- syscall -->
|
||
|
||
<dl id="syscall/js"><dt><a href="/pkg/syscall/js/">syscall/js</a></dt>
|
||
<dd>
|
||
<p><!-- CL 356430 -->
|
||
<code>Wrapper</code> interface has been removed.
|
||
</p>
|
||
</dd>
|
||
</dl><!-- syscall/js -->
|
||
|
||
<dl id="testing"><dt><a href="/pkg/testing/">testing</a></dt>
|
||
<dd>
|
||
<p><!-- CL 343883 -->
|
||
The precedence of <code>/</code> in the argument for <code>-run</code> and
|
||
<code>-bench</code> has been increased. <code>A/B|C/D</code> used to be
|
||
treated as <code>A/(B|C)/D</code> and is now treated as
|
||
<code>(A/B)/(C/D)</code>.
|
||
</p>
|
||
|
||
<p><!-- CL 356669 -->
|
||
If the <code>-run</code> option does not select any tests, the
|
||
<code>-count</code> option is ignored. This could change the behavior of
|
||
existing tests in the unlikely case that a test changes the set of subtests
|
||
that are run each time the test function itself is run.
|
||
</p>
|
||
</dd>
|
||
</dl><!-- testing -->
|
||
|
||
<dl id="text/template"><dt><a href="/pkg/text/template/">text/template</a></dt>
|
||
<dd>
|
||
<p><!-- CL 321490 -->
|
||
The <code>and</code> function no longer always evaluates all arguments; it
|
||
stops evaluating arguments after the first argument that evaluates to
|
||
false. Similarly, the <code>or</code> function now stops evaluating
|
||
arguments after the first argument that evaluates to true. This makes a
|
||
difference if any of the arguments is a function call.
|
||
</p>
|
||
</dd>
|
||
</dl><!-- text/template -->
|
||
|
||
<dl id="unicode/utf8"><dt><a href="/pkg/unicode/utf8/">unicode/utf8</a></dt>
|
||
<dd>
|
||
<p><!-- CL 345571 -->
|
||
The <a href="/pkg/unicode/utf8/#AppendRune"><code>AppendRune</code></a> function appends the UTF-8 new
|
||
encoding of a <code>rune</code> to a <code>[]byte</code>.
|
||
</p>
|
||
</dd>
|
||
</dl><!-- unicode/utf8 -->
|