I try brew upgrade go
it always show:
go 1.4.1 already installed
how can i upgrade go to 1.5?
Try running
brew update
brew upgrade
brew install go --cross-compile-common
brew upgrade might upgrade go alone without having to try to install it, after you run brew update/upgrade try running go version and see which version you have.
You should run brew update first, then run brew upgrade to upgrade all software installed by brew. Also you can run brew upgrade go to upgrade go only.