Libraries are ignored when goroot and gopath share the same prefix

[dbaumgarten]

If your go-root is (for example) /home/ubuntu/go and your gopath is /home/ubuntu/gopath, go-licenses will treat all dependencies as stdlib and therefore ignore them.

The issue lies here: https://github.com/google/go-licenses/blob/master/licenses/library.go#L204
When packages are stored inside the gopath, their path will start with /home/ubuntu/gopath, and as /home/ubuntu/go is a prefix of this, go-licenses thinks these packages belong to the stdlib.

The solution would be to append a path-seperator to build.Default.GOROOT (if it does not already end in one) before performing the prefix-check.