code: func (rm *responseModifier) Flush() {
  	flusher, ok := rm.rw.(http.Flusher)
  	if !ok {
  		logrus.Error("Internal response writer doesn't support the Flusher interface")
  		return
  	}
  
  	rm.FlushAll()
  	flusher.Flush()
  }
docs: // Flush uses the internal flush API of the wrapped http.ResponseWriter