Go 1.12 is not yet released. These are work-in-progress release notes. Go 1.12 is expected to be released in February 2019.
The latest Go release, version 1.12, arrives six months after Go 1.11. Most of its changes are in TODO. As always, the release maintains the Go 1 promise of compatibility. We expect almost all Go programs to continue to compile and run as before.
There are no changes to the language specification.
Go 1.12 is the last release that is supported on FreeBSD 10.x, which has already reached end-of-life. Go 1.13 will require FreeBSD 11.2+ or FreeBSD 12.0+.
Go 1.12 is the last release that will run on macOS 10.10 Yosemite. Go 1.13 will require macOS 10.11 El Capitan or later.
go tool vet no longer supported
The go vet command has been rewritten to serve as the
base for a range of different source code analysis tools. See
the golang.org/x/tools/go/analysis
package for details. A side-effect is that go tool vet
is no longer supported. External tools that use go tool
vet must be changed to use go
vet. Using go vet instead of go tool
vet should work with all supported versions of Go.
The build cache is now required as a step toward eliminating
$GOPATH/pkg. Setting the environment variable
GOCACHE=off to disable the
build cache
has no effect in Go 1.12.
The compiler's live variable analysis has improved. This may mean that
finalizers will be executed sooner in this release than in previous
releases. If that is a problem, consider the appropriate addition of a
runtime.KeepAlive call.
More functions are now eligible for inlining by default, including
functions that do nothing but call another function.
This extra inlining makes it additionally important to use
runtime.CallersFrames
instead of iterating over the result of
runtime.Callers directly.
// Old code which no longer works correctly (it will miss inlined call frames).
var pcs [10]uintptr
n := runtime.Callers(1, pcs[:])
for _, pc := range pcs[:n] {
f := runtime.FuncForPC(pc)
if f != nil {
fmt.Println(f.Name())
}
}
// New code which will work correctly.
var pcs [10]uintptr
n := runtime.Callers(1, pcs[:])
frames := runtime.CallersFrames(pcs[:n])
for {
frame, more := frames.Next()
fmt.Println(frame.Function)
if !more {
break
}
}
In Go 1.12, godoc no longer has a command-line interface and
is only a web server. Users should use go doc
for command-line help output instead.
All of the changes to the standard library are minor.
As always, there are various minor changes and updates to the library, made with the Go 1 promise of compatibility in mind.
TODO: https://golang.org/cl/149297: make Reader.Peek invalidate Unreads
TODO: https://golang.org/cl/61511: support frame-pointer for arm64
The new function ReplaceAll returns a copy of
a byte slice with all non-overlapping instances of a value replaced by another.
A pointer to a zero-value Reader is now
functionally equivalent to NewReader(nil).
Prior to Go 1.12, the former could not be used as a substitute for the latter in all cases.
TODO: https://golang.org/cl/138675: enable race detector on arm64
TODO: https://golang.org/cl/120055: use the new getrandom syscall on FreeBSD
TODO: https://golang.org/cl/139419: warn to stderr if blocked 60+ sec on first Reader.Read call
TODO: https://golang.org/cl/130397: remove assembler implementations
Maps are now printed in key-sorted order to ease testing. The ordering rules are:
reflect.Type describing the concrete type
and then by concrete value as described in the previous rules.
When printing maps, non-reflexive key values like NaN were previously
displayed as <nil>. As of this release, the correct values are printed.
TODO: https://golang.org/cl/146023: add "hurd" as a GOOS value
TODO: https://golang.org/cl/140958: add new mode bit PreserveAST to control clearing of data in AST
TODO: https://golang.org/cl/134075: add (*File).LineStart, which returns Pos for a given line
TODO: https://golang.org/cl/141397: remove CLI support
TODO: https://golang.org/cl/118755: make RegisterFormat safe for concurrent use
TODO: https://golang.org/cl/134235: pack image data for small bitdepth paletted images
TODO: https://golang.org/cl/149578: move GODEBUGCPU options into GODEBUG
TODO: https://golang.org/cl/130676: use F_FULLFSYNC fcntl for FD.Fsync on OS X
TODO: https://golang.org/cl/139457: export StringWriter
TODO: https://golang.org/cl/151299: update tzdata to 2018g
TODO: https://golang.org/cl/123157: add extended precision Add, Sub, Mul, Div
The
Dialer.DualStack setting is now ignored and deprecated;
RFC 6555 Fast Fallback ("Happy Eyeballs") is now enabled by default. To disable, set
Dialer.FallbackDelay to a negative value.
Similarly, TCP keep-alives are now enabled by default if
Dialer.KeepAlive is zero.
To disable, set it to a negative value.
On Linux, the splice system call is now used when copying from a
UnixConn to a
TCPConn.
The HTTP server now rejects misdirected HTTP requests to HTTPS servers with a plaintext "400 Bad Request" response.
The new Client.CloseIdleConnections
method calls the Client's underlying Transport's CloseIdleConnections
if it has one.
The Transport no longer rejects HTTP responses which declare
HTTP Trailers but don't use chunked encoding. Instead, the declared trailers are now just ignored.
The Transport no longer handles MAX_CONCURRENT_STREAMS values
advertised from HTTP/2 servers as strictly as it did during Go 1.10 and Go 1.11. The default behavior is now back
to how it was in Go 1.9: each connection to a server can have up to MAX_CONCURRENT_STREAMS requests
active and then new TCP connections are created as needed. In Go 1.10 and Go 1.11 the http2 package
would block and wait for requests to finish instead of creating new connections.
To get the stricter behavior back, import the
golang.org/x/net/http2 package
directly and set
Transport.StrictMaxConcurrentStreams to
true.
The ReverseProxy now automatically
proxies WebSocket requests.
The new ProcessState.ExitCode method
returns the process's exit code.
TODO: https://golang.org/cl/135075: add ModeCharDevice to ModeType
TODO: https://golang.org/cl/139418: add UserHomeDir
TODO: https://golang.org/cl/146020: add support for long path names on unix RemoveAll
TODO: https://golang.org/cl/145220: change IsAbs("NUL") to return true
TODO: https://golang.org/cl/33572: add Value.MapRange method and MapIter type
TODO: https://golang.org/cl/139783: add DeepEqual test
TODO: https://golang.org/cl/139784: add partial Deprecation comment to Copy
TODO: https://golang.org/cl/135395: use MADV_FREE on Linux if available
TODO: https://golang.org/cl/144220: add API to read module info in binary
The new function ReplaceAll returns a copy of
a string with all non-overlapping instances of a value replaced by another.
A pointer to a zero-value Reader is now
functionally equivalent to NewReader(nil).
Prior to Go 1.12, the former could not be used as a substitute for the latter in all cases.
The new Builder.Cap method returns the capacity of the builder's underlying byte slice.
TODO: https://golang.org/cl/131495: correctly handle invalid utf8 sequences in Map
TODO: https://golang.org/cl/125456: implement Unix Socket for Windows
TODO: https://golang.org/cl/138595: FreeBSD 12 ino64 support
TODO: https://golang.org/cl/141639: implement syscalls on Darwin using libSystem
TODO: https://golang.org/cl/147117: add Syscall18 on Windows
TODO: https://golang.org/cl/141644: add Wrapper interface to support external Value wrapper types
TODO: https://golang.org/cl/143137: make zero js.Value represent "undefined"
TODO: https://golang.org/cl/144384: add the Value.Truthy method
TODO: https://golang.org/cl/121936: exit with error if testing.Short is called before flag.Parse
TODO: https://golang.org/cl/139258: implement -benchtime=100x
TODO: https://golang.org/cl/142217: removed truncation of context in error message