code: func armorSeal(plaintext []byte, header string, footer string, params armorParams) (string, error) {
  	var buf bytes.Buffer
  	enc, err := newArmorEncoderStream(&buf, header, footer, params)
  	if err != nil {
  		return "", err
  	}
  	if _, err := enc.Write(plaintext); err != nil {
  		return "", err
  	}
  	if err := enc.Close(); err != nil {
  		return "", err
  	}
  	return buf.String(), nil
  }
docs: // armorSeal takes an input plaintext and returns and output armor encoding
  // as a string, or an error if a problem was encountered. Also provide a header
  // and a footer to frame the message.