code: func AcquireResponseRecorder(underline http.ResponseWriter) *ResponseRecorder {
  	v := rpool.Get()
  	var res *ResponseRecorder
  	if v != nil {
  		res = v.(*ResponseRecorder)
  	} else {
  		res = &ResponseRecorder{}
  	}
  	res.underline = underline
  	return res
  }
docs: // AcquireResponseRecorder returns a ResponseRecorder