Introduction

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.

Most users don't need to do this, and will instead install from precompiled binary packages as described in Getting Started, a much simpler process. If you want to help develop what goes into those precompiled packages, though, read on.

Install C tools, if needed

The Go tool chain is written in C. To build it, you need a C compiler installed. Please refer to the InstallFromSource page on the Go community Wiki for operating system specific instructions.

Install Git, if needed

To perform the next step you must have Git installed. (Check that you have a git command before proceeding.)

If you do not have a working Git installation, follow the instructions on the Git downloads page.

Fetch the repository

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 clone the repository and check out the latest release tag:

$ git clone https://go.googlesource.com/go
$ cd go
$ git checkout go1.4

(Optional) Switch to the master branch

If you intend to modify the go source code, and contribute your changes to the project, then move your repository off the release branch, and onto the master (development) branch. Otherwise, skip this step.

$ git checkout master

Install 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. ***

where the details on the last few lines reflect the operating system, architecture, and root directory used during the install.

Testing your installation

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.

Set up your work environment

You're almost done. You just need to do a little more setup.

How to Write Go Code Learn how to set up and use the Go tools

The How to Write Go Code document provides essential setup instructions for using the Go tools.

Install additional tools

The source code for several Go tools (including godoc) is kept in the go.tools repository. To install all of them, run the go get command:

$ go get golang.org/x/tools/cmd/...

Or if you just want to install a specific command (godoc in this case):

$ go get golang.org/x/tools/cmd/godoc

To install these tools, the go get command requires that Git be installed locally.

You must also have a workspace (GOPATH) set up; see How to Write Go Code for the details.

Note: The go command will install the godoc binary to $GOROOT/bin (or $GOBIN) and the cover and vet binaries to $GOROOT/pkg/tool/$GOOS_$GOARCH. You can access the latter commands with "go tool cover" and "go tool vet".

Community resources

The usual community resources such as #go-nuts on the Freenode IRC server and the Go Nuts mailing list have active developers that can help you with problems with your installation or your development work. For those who wish to keep up to date, there is another mailing list, golang-checkins, that receives a message summarizing each checkin to the Go repository.

Bugs can be reported using the Go issue tracker.

Keeping up with releases

New releases are announced on the golang-announce mailing list. Each announcement mentions the latest release tag, for instance, go1.4.

To update an existing tree to the latest release, you can run:

$ cd go/src
$ git fetch
$ git checkout <tag>
$ ./all.bash

Optional environment variables

The Go compilation environment can be customized by environment variables. None is required by the build, but you may wish to set some to override the defaults.

• $GOROOT

  The root of the Go tree, often $HOME/go. Its value is built into the tree when it is compiled, and defaults to the parent of the directory where all.bash was run. There is no need to set this unless you want to switch between multiple local copies of the repository.

• $GOROOT_FINAL

  The value assumed by installed binaries and scripts when $GOROOT is not set explicitly. It defaults to the value of $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 10.6 and above), dragonfly, freebsd, linux, netbsd, openbsd, plan9, solaris 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
  	dragonfly	386
  	dragonfly	amd64
  	freebsd	386
  	freebsd	amd64
  	freebsd	arm
  	linux	386
  	linux	amd64
  	linux	arm
  	netbsd	386
  	netbsd	amd64
  	netbsd	arm
  	openbsd	386
  	openbsd	amd64
  	plan9	386
  	plan9	amd64
  	solaris	amd64
  	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 Go 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. If $GOBIN is set, the go command installs all commands there.

• $GO386 (for 386 only, default is auto-detected if built on either 386 or amd64, 387 otherwise)

  This controls the code generated by 8g to use either the 387 floating-point unit (set to 387) or SSE2 instructions (set to sse2) for floating point computations.

  • GO386=387: use x87 for floating point operations; should support all x86 chips (Pentium MMX or later).
  • GO386=sse2: use SSE2 for floating point operations; has better performance than 387, but only available on Pentium 4/Opteron/Athlon 64 or later.
• $GOARM (for arm only; default is auto-detected if building on the target processor, 6 if not)

  This sets the ARM floating point co-processor architecture version the run-time should target. If you are compiling on the target system, its value will be auto-detected.

  • GOARM=5: use software floating point; when CPU doesn't have VFP co-processor
  • GOARM=6: use VFPv1 only; default if cross compiling; usually ARM11 or better cores (VFPv2 or better is also supported)
  • GOARM=7: use VFPv3; usually Cortex-A cores

  If in doubt, leave this variable unset, and adjust it if required when you first run the Go executable. The GoARM page on the Go community wiki contains further details regarding Go's ARM 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

although, to reiterate, none of these variables needs to be set to build, install, and develop the Go tree.