Go 1.13 is not yet released. These are work-in-progress release notes. Go 1.13 is expected to be released in August 2019.
As of Go 1.13, the go command by default downloads and authenticates modules using the Go module mirror and Go checksum database run by Google. See https://proxy.golang.org/privacy for privacy information about these services and the go command documentation for configuration details including how to disable the use of these servers or use different ones.
TODO
Per the number literal proposal, Go 1.13 supports a more uniform and modernized set of number literal prefixes.
0b or 0B indicates a binary integer literal
such as 0b1011.
0o or 0O indicates an octal integer literal
such as 0o660.
The existing octal notation indicated by a leading 0 followed by
octal digits remains valid.
0x or 0X may now be used to express the mantissa of a
floating-point number in hexadecimal format such as 0x1.0p-1021.
A hexadecimal floating-point number must always have an exponent, written as the letter
p or P followed by an exponent in decimal. The exponent scales
the mantissa by 2 to the power of the exponent.
i may now be used with any (binary, decimal, hexadecimal)
integer or floating-point literal.
1_000_000, 0b_1010_0110, or 3.1415_9265.
An underscore may appear between any two digits or the literal prefix and the first digit.
Per the signed shift counts proposal
Go 1.13 removes the restriction that a shift count
must be unsigned. This change eliminates the need for many artificial uint conversions,
solely introduced to satisfy this (now removed) restriction of the << and >> operators.
These language changes were implemented by changes to the compiler, and corresponding internal changes to the library
packages go/scanner and
text/scanner (number literals),
and go/types (signed shift counts).
If your code uses modules and your go.mod files specifies a language version, be sure
it is set to at least 1.13 to get access to these language changes.
You can do this by editing the go.mod file directly, or you can run
go mod edit -go=1.13.
AIX on PPC64 (aix/ppc64) now supports cgo, external
linking, and the c-archive and pie build
modes.
Go programs are now compatible with Android Q.
As announced in the Go 1.12 release notes, Go 1.13 now requires macOS 10.11 El Capitan or later; support for previous versions has been discontinued.
As announced in the Go 1.12 release notes, Go 1.13 now requires FreeBSD 11.2 or later; support for previous versions has been discontinued. FreeBSD 12.0 or later requires a kernel with the COMPAT_FREEBSD11 option set (this is the default).
Go now supports Illumos with GOOS=illumos.
The illumos build tag implies the solaris
build tag.
Go now supports NetBSD on arm64.
Go now supports OpenBSD on arm64.
The Windows version specified by internally-linked Windows binaries is now Windows 7 rather than NT 4.0. This was already the minimum required version for Go, but can affect the behavior of system calls that have a backwards-compatibility mode. These will now behave as documented. Externally-linked binaries (any program using cgo) have always specified a more recent Windows version.
go
get in module mode now supports the version suffix
@patch to request the latest patch release.
TODO(bcmills): expand.
When extracting a module from a version control system, the go
command now performs additional validation on the requested version string.
The +incompatible version annotation bypasses the requirement
of semantic
import versioning for repositories that predate the introduction of
modules. The go command now verifies that such a version does not
include an explicit go.mod file.
The go command now verifies the mapping
between pseudo-versions and
version-control metadata. Specifically:
vX.0.0.go command would generate. (For SHA-1 hashes as used
by git, a 12-digit prefix.)
If the main module directly requires a version that fails the above
validation, a corrected version can be obtained by redacting the version to
just the commit hash and re-running a go command such as go
list -m all or go mod tidy. For example,
require github.com/docker/docker v1.14.0-0.20190319215453-e7b5f7dbe98ccan be redacted to
require github.com/docker/docker e7b5f7dbe98cwhich resolves to
require github.com/docker/docker v0.7.3-0.20190319215453-e7b5f7dbe98c
If the main module has a transitive requirement on a version that fails
validation, the invalid version can still be replaced with a valid one through
the use of a replace
directive in the go.mod file of
the main module.
If the replacement is a commit hash, it will be resolved to the appropriate
pseudo-version. For example,
replace github.com/docker/docker v1.14.0-0.20190319215453-e7b5f7dbe98c => github.com/docker/docker e7b5f7dbe98cresolves to
replace github.com/docker/docker v1.14.0-0.20190319215453-e7b5f7dbe98c => github.com/docker/docker v0.7.3-0.20190319215453-e7b5f7dbe98c
The new go
build flag -trimpath removes all file system paths
from the compiled executable, to improve build reproducibility.
go
generate now sets the generate build tag so that
files may be searched for directives but ignored during build.
The compiler has a new implementation of escape analysis that is
more precise. For most Go code should be an improvement (in other
words, more Go variables and expressions allocated on the stack
instead of heap). However, this increased precision may also break
invalid code that happened to work before (for example, code that
violates
the unsafe.Pointer
safety rules). If you notice any regressions that appear
related, the old escape analysis pass can be re-enabled
with go build -gcflags=all=-newescape=false.
The option to use the old escape analysis will be removed in a
future release.
The compiler no longer emits floating point or complex constants
to go_asm.h files. These have always been emitted in a
form that could not be used as numeric constant in assembly code.
The assembler now supports many of the atomic instructions introduced in ARM v8.1.
gofmt (and with that go fmt) now canonicalizes
number literal prefixes and exponents to use lower-case letters, but
leaves hexadecimal digits alone. This improves readability when using the new octal prefix
(0O becomes 0o), and the rewrite is applied consistently.
gofmt now also removes unnecessary leading zeroes from a decimal integer
imaginary literal. (For backwards-compatibility, an integer imaginary literal
starting with 0 is considered a decimal, not an octal number.
Removing superfluous leading zeroes avoids potential confusion.)
For instance, 0B1010, 0XabcDEF, 0O660,
1.2E3, and 01i become 0b1010, 0xabcDEF,
0o660, 1.2e3, and 1i after applying gofmt.
godoc and go doc
The godoc webserver is no longer included in the main binary distribution.
To run the godoc webserver locally, manually install it first:
go get golang.org/x/tools/cmd/godoc godoc
The
go doc
command now always includes the package clause in its output, except for
commands. This replaces the previous behavior where a heuristic was used,
causing the package clause to be omitted under certain conditions.
Out of range panic messages now include the index that was out of
bounds and the length (or capacity) of the slice. For
example, s[3] on a slice of length 1 will panic with
"runtime error: index out of range [3] with length 1".
This release improves performance of most uses of defer
by 30%.
The runtime is now more aggressive at returning memory to the operating system to make it available to co-tenant applications. Previously, the runtime could retain memory for five or more minutes following a spike in the heap size. It will now begin returning it promptly after the heap shrinks. However, on many OSes, including Linux, the OS itself reclaims memory lazily, so process RSS will not decrease until the system is under memory pressure.
TODO generally
As announced in Go 1.12, Go 1.13 enables support for TLS 1.3 in the
crypto/tls package by default. It can be disabled by adding the
value tls13=0 to the GODEBUG
environment variable. The opt-out will be removed in Go 1.14.
See the Go 1.12 release notes for important compatibility information.
The new crypto/ed25519
package implements the Ed25519 signature
scheme. This functionality was previously provided by the
golang.org/x/crypto/ed25519
package, which becomes a wrapper for
crypto/ed25519 when used with Go 1.13+.
As always, there are various minor changes and updates to the library, made with the Go 1 promise of compatibility in mind.
TODO
The new ToValidUTF8 function returns a
copy of a given byte slice with each run of invalid UTF-8 byte sequences replaced by a given slice.
The formatting of contexts returned by WithValue no longer depends on fmt and will not stringify in the same way. Code that depends on the exact previous stringification might be affected.
Ed25519 certificates are now supported in TLS versions 1.2 and 1.3.
Ed25519 keys are now supported in certificates and certificate requests
according to RFC 8410, as well as by the
ParsePKCS8PrivateKey,
MarshalPKCS8PrivateKey,
and ParsePKIXPublicKey functions.
The paths searched for system roots now include /etc/ssl/cert.pem
to support the default location in Alpine Linux 3.7+.
The new NullTime type represents a time.Time that may be null.
The new NullInt32 type represents an int32 that may be null.
The Data.Type
method no longer panics if it encounters an unknown DWARF tag in
the type graph. Instead, it represents that component of the
type with
an UnsupportedType
object.
When using a <script> tag with "module" set as the
type attribute, code will now be interperted as JavaScript module script.
The scanner has been updated to recognize the new Go number literals, specifically
binary literals with 0b/0B prefix, octal literals with 0o/0O prefix,
and floating-point numbers with hexadecimal mantissa. The imaginary suffix i may now be used with any number
literal, and underscores may used as digit separators for grouping.
See the Changes to the language for details.
The type-checker has been updated to follow the new rules for integer shifts. See the Changes to the language for details.
The new Writer function returns the output destination for the standard logger.
The new Rat.SetUint64 method sets the Rat to a uint64 value.
Rat.SetString now accepts non-decimal floating point representations.
The execution time of Add,
Sub,
Mul,
RotateLeft, and
ReverseBytes is now
guaranteed to be independent of the inputs.
On Unix systems where use-vc is set in resolve.conf, TCP is used for DNS resolution.
The new field ListenConfig.KeepAlive
specifies the keep-alive period for network connections accepted by the listener.
The new field Transport.ForceAttemptHTTP2
controls whether HTTP/2 is enabled when a non-zero Dial, DialTLS, or DialContext
func or TLSClientConfig is provided.
When reusing HTTP/2, the Transport no longer performs unnecessary TLS handshakes.
TimeoutHandler's
ResponseWriter now implements the
Pusher and Flusher interfaces.
The new Server fields
BaseContext and
ConnContext
allow finer control over the Context values provided to requests and connections.
The new UserConfigDir function
returns the default directory to use for user-specific configuration data.
If a File is opened using the O_APPEND flag, its
WriteAt method will always return an error.
On Windows, the environment for a Cmd always inherits the
%SYSTEMROOT% value of the parent process unless the
Cmd.Env field includes an explicit value for it.
The new Value.IsZero method reports whether a Value is the zero value for its type.
The MakeFunc function now allows assignment conversions on returned values, instead of requiring exact type match. This is particularly useful when the type being returned is an interface type, but the value actually returned is a concrete value implementing that type.
Tracebacks, runtime.Caller,
and runtime.Callers now refer to the function that
initializes the global variables of PKG
as PKG.init instead of PKG.init.ializers
The new ToValidUTF8 function returns a
copy of a given string with each run of invalid UTF-8 byte sequences replaced by a given string.
Large Pool no longer increase stop-the-world pause times.
Pool no longer needs to be completely repopulated after every GC. It now retains some objects across GCs,
as opposed to releasing all objects, reducing load spikes for heavy users of Pool.
Uses of _getdirentries64 have been removed from Darwin builds, to allow binaries
built with 1.12 to be uploaded to the macOS App Store.
The new ProcessAttributes and ThreadAttributes fields in
SysProcAttr have been introduced for Windows,
exposing security settings when creating new processes.
EINVAL is no longer returned in zero
Chmod mode on Windows.
TypedArrayOf has been replaced by
CopyBytesToGo and
CopyBytesToJS for copying bytes between a byte slice and a Uint8Array.
When running benchmarks, B.N is no longer rounded.
The new method B.ReportMetric lets users report
custom benchmark metrics and override built-in metrics.
Testing flags are now registered in the new Init function.
As a result, testing flags are now only registered when running a test binary.
The scanner has been updated to recognize the new Go number literals, specifically
binary literals with 0b/0B prefix, octal literals with 0o/0O prefix,
and floating-point numbers with hexadecimal mantissa.
Also, the new AllowDigitSeparators
mode allows number literals to contain underscores as digit separators (off by default for backwards-compatibility).
See the Changes to the language for details.
The new slice function returns the result of slicing its first argument by the following arguments.
Day-of-year is now supported by Format
and Parse.
The new Duration methods
Microseconds and
Milliseconds return
the duration as an integer count of their respectively named units.