code: func compress(data []byte) ([]byte, error) {
  	var buf bytes.Buffer
  	w := gzip.NewWriter(&buf)
  	if _, err := w.Write(data); err != nil {
  		return nil, err
  	}
  	if err := w.Close(); err != nil {
  		return nil, err
  	}
  	return buf.Bytes(), nil
  }
docs: // compress compresses data with gzip.