code: func (rm *responseModifier) CloseNotify() <-chan bool {
  	closeNotifier, ok := rm.rw.(http.CloseNotifier)
  	if !ok {
  		logrus.Error("Internal response writer doesn't support the CloseNotifier interface")
  		return nil
  	}
  	return closeNotifier.CloseNotify()
  }
docs: // CloseNotify uses the internal close notify API of the wrapped http.ResponseWriter