I'm using gotest for testing, my testing is really primitive right now, no mocking frameworks. The only non-standard library I'm using is gorilla/mux for routing. Go feels a little verbose and restrictive coming from Python, but after being acclimated, I love it. It's extremely productive, performance is nice, deployment is so easy. The pain points for me were understanding the package system and structuring my project, which I worked through eventually.