Golang: Installation directory error?

I have the error:

go install: no install location for directory /Users/xwilly/Dropbox/go/project/src outside GOPATH 

I'm using go version 1.1 on OS X.

I can build & run but can't install packages.

My environment:

GOPATH=/Users/xwilly/Dropbox/go/project
PATH=/Library/Frameworks/Python.framework/Versions/2.7/bin:/usr/bin:/bin:/usr/sbin:/sbin:/usr/local/bin:/usr/local/go/bin:/Users/xwilly/Dropbox/go/project/bin

Project tree:

/Users/xwilly/Dropbox/go/project
bin
pkg
src

I can build without error:

..:src xwilly$ go build test.go 
..:src xwilly$ go install test.go
go install: no install location for directory /Users/xwilly/Dropbox/go/project/src outside GOPATH

Here is a simple example:

xwilly$ cat test.go 
package main
import (
    "fmt"
)
func main() {
    fmt.Println("Bonjour")
}
xwilly$ go run test.go 
Bonjour
xwilly$ go install test.go 
go install: no install location for directory /Users/xwilly/Dropbox/go/project/src/learning outside GOPATH

> [Command go][1]
>
> [GOPATH environment variable][2]
>
> Each directory listed in GOPATH must have a prescribed structure:
>
> The src/ directory holds source code. The path below 'src' determines
> the import path or executable name.
>
> The pkg/ directory holds installed package objects. As in the Go tree,
> each target operating system and architecture pair has its own
> subdirectory of pkg (pkg/GOOS_GOARCH).
>
> If DIR is a directory listed in the GOPATH, a package with source in
> DIR/src/foo/bar can be imported as "foo/bar" and has its compiled form
> installed to "DIR/pkg/GOOS_GOARCH/foo/bar.a".
>
> The bin/ directory holds compiled commands. Each command is named for
> its source directory, but only the final element, not the entire path.
> That is, the command with source in DIR/src/foo/quux is installed into
> DIR/bin/quux, not DIR/bin/foo/quux. The foo/ is stripped so that you
> can add DIR/bin to your PATH to get at the installed commands. If the
> GOBIN environment variable is set, commands are installed to the
> directory it names instead of DIR/bin.
>
> Here's an example directory layout:
>
> GOPATH=/home/user/gocode
>
> /home/user/gocode/
> src/
> foo/
> bar/ (go code in package bar)
> x.go
> quux/ (go code in package main)
> y.go
> bin/
> quux (installed command)
> pkg/
> linux_amd64/
> foo/
> bar.a (installed package object)

Your directory structure is wrong. You are trying to install a command (package main). It should be in a source directory named after your command. See the quux command above.

In your case, assume your command is going to be named billy.

$ mkdir -p /Users/xwilly/Dropbox/go/project/src/billy

which is inside your GOPATH. Move your test.go file to this directory. Run

$ go install billy

The command billy should, unless you have set GOBIN, be installed in the

/Users/xwilly/Dropbox/go/project/bin

directory inside your GOPATH, which should be in your PATH.
[1]: http://golang.org/cmd/go/
[2]: http://golang.org/cmd/go/#hdr-GOPATH_environment_variable