I'll stop with the golang tips shortly, but another quick time saver incase you've not seen this before: you can use direnv to manage your GOPATH settings for each of your projects.
direnv is a small utility that will set/unset environmental variables as you enter/leave directories. It's dead easy to set up, and in homebrew if you're on a Mac. This means I can set a GOPATH specifically for each go project, without having to remember to do GOPATH=$PWD each time - direnv just sets it as a change directory to the project, and unsets it when I move away.
This can be useful for other things to, like setting PYTHONPATH or other project specific environmental variables.
Hat tip to Day Barr for alerting me to that one.