code: func (resp *Response) WriteGzipLevel(w *bufio.Writer, level int) error {
  	if err := resp.gzipBody(level); err != nil {
  		return err
  	}
  	return resp.Write(w)
  }
docs: // WriteGzipLevel writes response with gzipped body to w.
  //
  // Level is the desired compression level:
  //
  //     * CompressNoCompression
  //     * CompressBestSpeed
  //     * CompressBestCompression
  //     * CompressDefaultCompression
  //     * CompressHuffmanOnly
  //
  // The method gzips response body and sets 'Content-Encoding: gzip'
  // header before writing response to w.
  //
  // WriteGzipLevel doesn't flush response to w for performance reasons.