GOPATH.md - wiki - Git at Google

 # Introduction

 The GOPATH environment variable is used to specify directories outside of $GOROOT that contain the source for Go projects and their binaries.

 See the [go command](http://golang.org/cmd/go/#hdr-GOPATH_environment_variable) and [go/build package](http://golang.org/pkg/go/build/) documentation for more details.

 Since the $GOPATH variable can be a list, the rest of this document will use $GOPATH to mean the first element unless otherwise specified.

 ## Integrating GOPATH

 On OS X or Linux (bash), adding the following expression to PATH will add all $GOPATH/bin directories.
 ```
 ${GOPATH//://bin:}/bin
 ```

 ## Directory layout

 The source for a package with the import path ` "X/Y/Z" ` is in the directory
 ```
 $GOPATH/src/X/Y/Z
 ```

 The binary for a package with the import path ` "X/Y/Z" ` is in
 ```
 $GOPATH/pkg/$GOOS_$GOARCH/X/Y/Z.a
 ```

 The binary for a command whose source is in ` $GOPATH/src/A/B ` is
 ```
 $GOPATH/bin/B
 ```

 ## Repository Integration and Creating "go gettable" Projects
 When fetching a package the go tool looks at the package's import path to discover a URL. For instance, if you attempt to
 ```
 go get code.google.com/p/gomatrix/matrix
 ```
 the go tool will get the source from the project hosted at http://code.google.com/p/gomatrix/. It will clone the repository to
 ```
 $GOPATH/src/code.google.com/p/gomatrix
 ```

 As a result, if (from your repository project) you import a package that is in the same repository, you need to use its "full" import path - the place "go get" puts it. In this example, if something else wants to import the "matrix" package, it should import "code.google.com/p/gomatrix/matrix" rather than "matrix".

 ## Tips and tricks

 ### Third-party Packages
 It is useful to have two GOPATH entries. One for a location for 3rd party goinstalled packages, and the second for your own projects. List the 3rd party GOPATH first, so that goinstall will use it as a default destination. Then you can work in the second GOPATH directory and have all your packages be importable by using the "go" command, goinstall, or a GOPATH-aware 3rd party build tool like [gb](http://code.google.com/p/go-gb).

 ## FAQ
 ### Why won't ` $GOPATH/src/cmd/mycmd/*.go ` build?
 When the go command is looking for packages, it always looks in ` $GOROOT ` first.  This includes directories, so if it finds (as in the case above) a ` cmd/ ` directory in ` $GOROOT ` it won't proceed to look in any of the GOPATH directories.  This prevents you from defining your own ` math/matrix ` package as well as your own ` cmd/mycmd ` commands.
	# Introduction

	The GOPATH environment variable is used to specify directories outside of $GOROOT that contain the source for Go projects and their binaries.

	See the [go command](http://golang.org/cmd/go/#hdr-GOPATH_environment_variable) and [go/build package](http://golang.org/pkg/go/build/) documentation for more details.

	Since the $GOPATH variable can be a list, the rest of this document will use $GOPATH to mean the first element unless otherwise specified.

	## Integrating GOPATH

	On OS X or Linux (bash), adding the following expression to PATH will add all $GOPATH/bin directories.
	```
	${GOPATH//://bin:}/bin
	```

	## Directory layout

	The source for a package with the import path ` "X/Y/Z" ` is in the directory
	```
	$GOPATH/src/X/Y/Z
	```

	The binary for a package with the import path ` "X/Y/Z" ` is in
	```
	$GOPATH/pkg/$GOOS_$GOARCH/X/Y/Z.a
	```

	The binary for a command whose source is in ` $GOPATH/src/A/B ` is
	```
	$GOPATH/bin/B
	```

	## Repository Integration and Creating "go gettable" Projects
	When fetching a package the go tool looks at the package's import path to discover a URL. For instance, if you attempt to
	```
	go get code.google.com/p/gomatrix/matrix
	```
	the go tool will get the source from the project hosted at http://code.google.com/p/gomatrix/. It will clone the repository to
	```
	$GOPATH/src/code.google.com/p/gomatrix
	```

	As a result, if (from your repository project) you import a package that is in the same repository, you need to use its "full" import path - the place "go get" puts it. In this example, if something else wants to import the "matrix" package, it should import "code.google.com/p/gomatrix/matrix" rather than "matrix".

	## Tips and tricks

	### Third-party Packages
	It is useful to have two GOPATH entries. One for a location for 3rd party goinstalled packages, and the second for your own projects. List the 3rd party GOPATH first, so that goinstall will use it as a default destination. Then you can work in the second GOPATH directory and have all your packages be importable by using the "go" command, goinstall, or a GOPATH-aware 3rd party build tool like [gb](http://code.google.com/p/go-gb).

	## FAQ
	### Why won't ` $GOPATH/src/cmd/mycmd/*.go ` build?
	When the go command is looking for packages, it always looks in ` $GOROOT ` first. This includes directories, so if it finds (as in the case above) a ` cmd/ ` directory in ` $GOROOT ` it won't proceed to look in any of the GOPATH directories. This prevents you from defining your own ` math/matrix ` package as well as your own ` cmd/mycmd ` commands.