Update, as of Go 1.8: If you’re installing Go 1.8 (released: Feb 2017) or later, GOPATH is automatically determined by the Go toolchain for you.
It defaults to $HOME/go on macOS (nee OS X) – e.g. /Users/matt/go/. This makes getting started with Go even easier, and you can go get <package> right after installing Go.
For the shell: (the manual method)
~/.bash_profile should contain export GOPATH=$HOME/go and also export PATH=$GOPATH/bin:$PATH. The use of the $ is important: make sure to note where I’ve used it (and where I have not).
For Sublime Text:
Sublime Text menu > Preferences > Package Settings > GoSublime > Settings: User
{
"shell": ["/bin/bash"],
"env": {"GOPATH": "/Users/#USERNAME#/go/"},
}
Make sure your GOPATH is not set to the full path of the package; just the root of your go folder where src, pkg, and bin reside. If you’re not using GoSublime, I’d suggest installing that first.