Following up on comments; I gave gobot another go for the sample opencv_face_detect and it works for me. Although the example link you posted seems to be faulty/outdated.
This is on OS X 10.11.5 and go1.6.2 darwin/amd64.
Here are the steps I did;
brew tap homebrew/science && brew install opencv
Install gobot and go-opencv;
go get github.com/hybridgroup/gobot && go get github.com/lazywei/go-opencv
Run the face_detect example located at "github.com/hybridgroup/gobot/examples" and don't forget to smile!
go run opencv_face_detect.go