http.go
func (resp *Response) WriteGzip(w *bufio.Writer) error {
	return resp.WriteGzipLevel(w, CompressDefaultCompression)
}
func (resp *Response) WriteGzip(w *bufio.Writer) error {
	return resp.WriteGzipLevel(w, CompressDefaultCompression)
}
// WriteGzip writes response with gzipped body to w.
//
// The method gzips response body and sets 'Content-Encoding: gzip'
// header before writing response to w.
//
// WriteGzip doesn't flush response to w for performance reasons.