entr: run go test on any file change

entr: Event Notify Test Runner.

A utility for running arbitrary commands when files change. Uses kqueue(2) or inotify(7) to avoid polling.  entrwas written to make rapid feedback and automated testing natural and completely ordinary.

# install
brew install entr
source ~/.zshrc

# run and watch go tests
cd <somewhere_with_go_tests>
entr -c bash -c "clear; go test $*" < <(find .)