Go is an open source project, distributed under a BSD-style license. This document explains how to check out the sources, build them on your own machine, and run them.
There are two official Go compiler tool chains.
This document focuses on the gc Go
compiler and tools (6g, 8g etc.).
For information on how to use gccgo, a more traditional
compiler using the GCC back end, see
Setting up and using gccgo.
The Go compilers support three instruction sets. There are important differences in the quality of the compilers for the different architectures.
amd64 (a.k.a. x86-64); 6g,6l,6c,6a
gccgo can do noticeably better sometimes).
386 (a.k.a. x86 or x86-32); 8g,8l,8c,8a
amd64 port.
arm (a.k.a. ARM); 5g,5l,5c,5a
Except for things like low-level operating system interface code, the run-time support is the same in all ports and includes a mark-and-sweep garbage collector, efficient array and string slicing, and support for efficient goroutines, such as stacks that grow and shrink on demand.
The compilers can target the FreeBSD, Linux, NetBSD, OpenBSD, OS X (Darwin), and Windows operating systems. The full set of supported combinations is listed in the discussion of environment variables below.
The Go tool chain is written in C. To build it, you need a C compiler installed.
On OS X, a C compiler can be installed as part of Xcode.
On Ubuntu/Debian, use sudo apt-get install gcc libc6-dev.
If you want to build 32-bit binaries on a 64-bit system you'll also need the
libc6-dev-i386 package.
TODO: add Windows compiler info
To perform the next step you must have Mercurial installed. (Check that you
have an hg command.) This suffices to install Mercurial on most
systems:
sudo easy_install mercurial==2.0
On Ubuntu/Debian, the Mercurial in your distribution's package repository is most likely old and broken. You might try this first:
apt-get install python-setuptools python-dev build-essential
If that fails, try installing manually from the Mercurial Download page.
Mercurial versions 1.7.x and up require the configuration of Certification Authorities (CAs). Error messages of the form:
warning: code.google.com certificate with fingerprint b1:af: ... bc not verified (check hostfingerprints or web.cacerts config setting)
when using Mercurial indicate that the CAs are missing.
Check your Mercurial version (hg --version) and
configure the CAs
if necessary.
Go will install to a directory named go.
Change to the directory that will be its parent
and make sure the go directory does not exist.
Then check out the repository:
$ hg clone -u release https://code.google.com/p/go
To build the Go distribution, run
$ cd go/src $ ./all.bash
(To build under Windows use all.bat.)
If all goes well, it will finish by printing output like:
ALL TESTS PASSED --- Installed Go for linux/amd64 in /home/you/go. Installed commands in /home/you/go/bin. *** You need to add /home/you/go/bin to your $PATH. *** The compiler is 6g.
where the details on the last few lines reflect the operating system, architecture, and root directory used during the install.
For more information about ways to control the build, see the discussion of environment variables below.
Check that Go is installed correctly by building a simple program.
Create a file named hello.go and put the following program in it:
package main
import "fmt"
func main() {
fmt.Printf("hello, world\n")
}
Then run it with the go tool:
$ go run hello.go hello, world
If you see the "hello, world" message then Go is installed correctly.
Start by taking A Tour of Go or reading the Go Tutorial.
For more detail about the process of building and testing Go programs read How to Write Go Code.
Build a web application by following the Wiki Codelab.
Read Effective Go to learn about writing idiomatic Go code.
For the full story, consult Go's extensive documentation.
For real-time help, there may be users or developers on
#go-nuts on the Freenode IRC server.
The official mailing list for discussion of the Go language is Go Nuts.
Bugs can be reported using the Go issue tracker.
For those who wish to keep up with development, there is another mailing list, golang-checkins, that receives a message summarizing each checkin to the Go repository.
The Go project maintains two stable tags in its Mercurial repository:
release and weekly.
The weekly tag is updated about once a week, and should be used by
those who want to track the project's development.
The release tag is given, less often, to those weekly releases
that have proven themselves to be robust.
Most Go users will want to keep their Go installation at the latest
release tag.
New releases are announced on the
golang-announce
mailing list.
To update an existing tree to the latest release, you can run:
$ cd go/src $ hg pull $ hg update release $ ./all.bash
To use the weekly tag run hg update weekly instead.
The Go compilation environment can be customized by environment variables. None are required by the build, but you may wish to set them to override the defaults.
$GOROOT
The root of the Go tree, often $HOME/go.
This defaults to the parent of the directory where all.bash is run.
If you choose not to set $GOROOT, you must
run gomake instead of make or gmake
when developing Go programs using the conventional makefiles.
$GOROOT_FINAL
The value assumed by installed binaries and scripts when
$GOROOT is not set.
It defaults to the value used for $GOROOT.
If you want to build the Go tree in one location
but move it elsewhere after the build, set
$GOROOT_FINAL to the eventual location.
$GOOS and $GOARCH
The name of the target operating system and compilation architecture.
These default to the values of $GOHOSTOS and
$GOHOSTARCH respectively (described below).
Choices for $GOOS are
darwin (Mac OS X 10.5 and above), freebsd,
linux, netbsd, openbsd,
plan9, and windows.
Choices for $GOARCH are
amd64 (64-bit x86, the most mature port),
386 (32-bit x86), and arm (32-bit ARM).
The valid combinations of $GOOS and $GOARCH are:
$GOOS | $GOARCH | ||
|---|---|---|---|
darwin | 386 |
||
darwin | amd64 |
||
freebsd | 386 |
||
freebsd | amd64 |
||
linux | 386 |
||
linux | amd64 |
||
linux | arm |
||
netbsd | 386 |
||
netbsd | amd64 |
||
openbsd | 386 |
||
openbsd | amd64 |
||
plan9 | 386 |
||
windows | 386 |
||
windows | amd64 |
$GOHOSTOS and $GOHOSTARCH
The name of the host operating system and compilation architecture. These default to the local system's operating system and architecture.
Valid choices are the same as for $GOOS and
$GOARCH, listed above.
The specified values must be compatible with the local system.
For example, you should not set $GOHOSTARCH to
arm on an x86 system.
$GOBIN
The location where binaries will be installed.
The default is $GOROOT/bin.
After installing, you will want to arrange to add this
directory to your $PATH, so you can use the tools.
$GOARM (arm, default=6)
The ARM architecture version the run-time libraries should target.
Setting $GOARM to 5 causes the linker to emit calls
to a software floating point implementation instead of using
hardware floating point support.
Note that $GOARCH and $GOOS identify the
target environment, not the environment you are running on.
In effect, you are always cross-compiling.
By architecture, we mean the kind of binaries
that the target environment can run:
an x86-64 system running a 32-bit-only operating system
must set GOARCH to 386,
not amd64.
If you choose to override the defaults,
set these variables in your shell profile ($HOME/.bashrc,
$HOME/.profile, or equivalent). The settings might look
something like this:
export GOROOT=$HOME/go export GOARCH=amd64 export GOOS=linux