GOPATH specifies the location of your go workspace. By default this will be $HOME/go.
You should set your $GOPATH in .zshrc or .bash_profile to be used later in scripts or shell.
Add the followings into your .bash_profile:
export GOPATH=$HOME/go
export PATH=$PATH:$GOPATH/bin
Reload your shell and done.
To confirm that it’s working, enter $GOPATH in your shell and it should take you to the go workspace directory.