mkdir $HOME/go
mkdir -p $HOME/go/src/github.com/YOUR_USERNAME
-p
means to create intermediate directories as required.
export GOPATH=$HOME/go
export GOROOT=/usr/local/opt/go/libexec
export PATH=$PATH:$GOPATH/bin
export PATH=$PATH:$GOROOT/bin
brew install go
go get golang.org/x/tools/cmd/godoc