code: func NewResponseWriter(rw http.ResponseWriter) ResponseWriter {
  	nrw := &responseWriter{
  		ResponseWriter: rw,
  	}
  
  	if _, ok := rw.(http.CloseNotifier); ok {
  		return &responseWriterCloseNotifer{nrw}
  	}
  
  	return nrw
  }
docs: // NewResponseWriter creates a ResponseWriter that wraps an http.ResponseWriter