Go 1.17 is not yet released. These are work-in-progress release notes. Go 1.17 is expected to be released in August 2021.
TODO: https://golang.org/cl/216424: allow conversion from slice to array ptr
TODO: https://golang.org/cl/312212: add unsafe.Add and unsafe.Slice
As announced in the Go 1.16 release notes, Go 1.17 requires macOS 10.13 High Sierra or later; support for previous versions has been discontinued.
Go 1.17 adds support of 64-bit ARM architecture on Windows (the
windows/arm64 port). This port supports cgo.
The 64-bit MIPS architecture on OpenBSD (the openbsd/mips64
port) now supports cgo.
In Go 1.16, on the 64-bit x86 and 64-bit ARM architectures on
OpenBSD (the openbsd/amd64 and openbsd/arm64
ports) system calls are made through libc, instead
of directly using the machine instructions. In Go 1.17, this is
also done on the 32-bit x86 and 32-bit ARM architectures on OpenBSD
(the openbsd/386 and openbsd/arm ports).
This ensures forward-compatibility with future versions of
OpenBSD.
TODO: complete the Ports section
TODO: complete the Tools section
If a module specifies go 1.17 or higher in its
go.mod file, its transitive requirements are now loaded lazily,
avoiding the need to download or read go.mod files for
otherwise-irrelevant dependencies. To support lazy loading, in Go 1.17 modules
the go command maintains explicit requirements in
the go.mod file for every dependency that provides any package
transitively imported by any package or test within the module.
See the design
document for more detail.
To facilitate the upgrade to lazy loading,
the go mod tidy subcommand now supports
a -go flag to set or change the go version in
the go.mod file. To enable lazy loading for an existing module
without changing the selected versions of its dependencies, run:
go mod tidy -go=1.17
TODO: Describe the -compat flag
for go mod tidy.
Module authors may deprecate a module by adding a
// Deprecated:
comment to go.mod, then tagging a new version.
go get now prints a warning if a module needed to
build packages named on the command line is deprecated. go
list -m -u prints deprecations for all
dependencies (use -f or -json to show the full
message). The go command considers different major versions to
be distinct modules, so this mechanism may be used, for example, to provide
users with migration instructions for a new major version.
go get
The go get -insecure flag is
deprecated and has been removed. To permit the use of insecure schemes
when fetching dependencies, please use the GOINSECURE
environment variable. The -insecure flag also bypassed module
sum validation, use GOPRIVATE or GONOSUMDB if
you need that functionality. See go help
environment for details.
go.mod files missing go directives
If the main module's go.mod file does not contain
a go directive and
the go command cannot update the go.mod file, the
go command now assumes go 1.11 instead of the
current release. (go mod init has added
go directives automatically since
Go 1.12.)
If a module dependency lacks an explicit go.mod file, or
its go.mod file does not contain
a go directive,
the go command now assumes go 1.16 for that
dependency instead of the current release. (Dependencies developed in GOPATH
mode may lack a go.mod file, and
the vendor/modules.txt has to date never recorded
the go versions indicated by dependencies' go.mod
files.)
vendor contents
If the main module specifies go 1.17 or higher,
go mod vendor now annotates
vendor/modules.txt with the go version indicated by
each vendored module in its own go.mod file. The annotated
version is used when building the module's packages from vendored source code.
If the main module specifies go 1.17 or higher,
go mod vendor now omits go.mod
and go.sum files for vendored dependencies, which can otherwise
interfere with the ability of the go command to identify the correct
module root when invoked within the vendor tree.
The go command by default now suppresses SSH password prompts and
Git Credential Manager prompts when fetching Git repositories using SSH, as it
already did previously for other Git password prompts. Users authenticating to
private Git repos with password-protected SSH may configure
an ssh-agent to enable the go command to use
password-protected SSH keys.
go mod download
When go mod download is invoked without
arguments, it will no longer save sums for downloaded module content to
go.sum. It may still make changes to go.mod and
go.sum needed to load the build list. This is the same as the
behavior in Go 1.15. To save sums for all modules, use go
mod download all.
TODO: https://golang.org/cl/249759: cmd/cover: replace code using optimized golang.org/x/tools/cover
TODO: https://golang.org/cl/299532: cmd/vet: bring in sigchanyzer to report unbuffered channels to signal.Notify
TODO: complete the Vet section
TODO: https://golang.org/cl/304470: cmd/compile, runtime: add metadata for argument printing in traceback
TODO: complete the Runtime section
Functions containing closures can now be inlined. One effect of this change is that a function with a closure may actually produce a distinct closure function for each place that the function is inlined. Hence, this change could reveal bugs where Go functions are compared (incorrectly) by pointer value. Go functions are by definition not comparable. TODO: complete the Compiler section, or delete if not needed
TODO: complete the Linker section, or delete if not needed
TODO: complete the Core library section
(*Conn).HandshakeContext was added to allow the user to control cancellation of an in-progress TLS Handshake. The context provided is propagated into the ClientHelloInfo and CertificateRequestInfo structs and accessible through the new (*ClientHelloInfo).Context and (*CertificateRequestInfo).Context methods respectively. Canceling the context after the handshake has finished has no effect.
When Config.NextProtos is set, servers now
enforce that there is an overlap between the configured protocols and the protocols
advertised by the client, if any. If there is no overlap the connection is closed
with the no_application_protocol alert, as required by RFC 7301.
The runtime/cgo package now provides a new facility that allows to turn any Go values to a safe representation that can be used to pass values between C and Go safely. See runtime/cgo.Handle for more information.
As always, there are various minor changes and updates to the library, made with the Go 1 promise of compatibility in mind.
The new methods File.OpenRaw, Writer.CreateRaw, Writer.Copy provide support for cases where performance is a primary concern.
The Writer.WriteRune method
now writes the replacement character U+FFFD for negative rune values,
as it does for other invalid runes.
The Buffer.WriteRune method
now writes the replacement character U+FFFD for negative rune values,
as it does for other invalid runes.
The new
Reader.Reset
and
Writer.Reset
methods allow reuse of a Reader or Writer.
TODO: https://golang.org/cl/302230: fix salt length calculation with PSSSaltLengthAuto
The DB.Close method now closes
the connector field if the type in this field implements the
io.Closer interface.
The new
NullInt16
and
NullByte
structs represent the int16 and byte values that may be null. These can be used as
destinations of the Scan method,
similar to NullString.
binary.Uvarint will stop reading after 10 bytes to avoid
wasted computations. If more than 10 bytes are needed, the byte count returned is -11.
Previous Go versions could return larger negative counts when reading incorrectly encoded varints.
TODO: https://golang.org/cl/271788: panic if flag name begins with - or contains =
The new FileInfoToDirEntry function converts a FileInfo to a DirEntry.
The math package now defines three more constants: MaxUint, MaxInt and MinInt.
For 32-bit systems their values are 2^32 - 1, 2^31 - 1 and -2^31, respectively.
For 64-bit systems their values are 2^64 - 1, 2^63 - 1 and -2^63, respectively.
TODO: https://golang.org/cl/305230: support reading shared mime-info database on unix systems
TODO: https://golang.org/cl/272668: add IP.IsPrivate
TODO: https://golang.org/cl/301709: make go resolver aware of network parameter
TODO: https://golang.org/cl/307030: make ErrClosed and ParseError implement net.Error
The net/http package now uses the new
(*tls.Conn).HandshakeContext
with the Request context
when performing TLS handshakes in the client or server.
TODO: https://golang.org/cl/235437: add to deadlines only when positive
The ReadRequest function
now returns an error when the request has multiple Host headers.
TODO: https://golang.org/cl/308950: panic on non-3 digit (XXX) status code in Recorder.WriteHeader
TODO: https://golang.org/cl/314850: add Values.Has
The File.WriteString method
has been optimized to no longer make a copy of the input string.
The new
StructField.IsExported
and
Method.IsExported
methods report whether a struct field or type method is exported.
They provide a more readable alternative to checking whether PkgPath
is empty.
TODO: https://golang.org/cl/281233: add VisibleFields function
TODO: https://golang.org/cl/284136: panic if ArrayOf is called with negative length
TODO: https://golang.org/cl/170079: implement Ryū-like algorithm for fixed precision ftoa
TODO: https://golang.org/cl/170080: Implement Ryū algorithm for ftoa shortest mode
The new QuotedPrefix function
returns the quoted string (as understood by
Unquote)
at the start of input.
The Builder.WriteRune method
now writes the replacement character U+FFFD for negative rune values,
as it does for other invalid runes.
atomic.Value now has Swap and
CompareAndSwap methods that provide
additional atomic operations.
TODO: https://golang.org/cl/295371: do not overflow key memory in GetQueuedCompletionStatus
TODO: https://golang.org/cl/313653: restore signal mask after setting foreground process group
TODO: https://golang.org/cl/310033: add -shuffle=off|on|N to alter the execution order of tests and benchmarks
TODO: https://golang.org/cl/301493: add a mode to skip func-check on parsing
The Time type now has a
GoString method that
will return a more useful value for times when printed with the
%#v format specifier in the fmt package.
TODO: https://golang.org/cl/264077: add Time.IsDST() to check if its Location is in Daylight Savings Time
TODO: https://golang.org/cl/293349: add Time.Unix{Milli,Micro} and to-Time helpers UnixMicro, UnixMilli
TODO: https://golang.org/cl/300996: support "," as separator for fractional seconds