I have tried several times to fix this problem in the past 5 or 6 years, once with symlinks (which would break quite often -- it's unsurprising that Plan 9 developers wouldn't care too much for handling symlinks correctly :P).
The current way I handle it is that $HOME/.local is my GOPATH, and $HOME/src links to $HOME/.local/src. So you can just have $HOME/src/github.com/bar/foo -- which is less ideal than just $HOME/src/foo, but it's something at least.