I know it's unfortunately long, but I have yet to find someone who has read it and is still confused about $GOPATH.
Part of it is just understanding how to set up the $GOPATH. Understanding its structure is one thing, but actually getting the 'go' to read the right directory on OSX vs Ubuntu vs other systems depending on your shell (and version of go?) and over old installations, can be a very confusing way to start using the language.