code: func PKCS7Pad(data []byte, blockSize int) ([]byte, error) {
  	length := len(data)
  	padLen := blockSize - (length % blockSize)
  	padText := bytes.Repeat([]byte{byte(padLen)}, padLen)
  	return append(data, padText...), nil
  }
docs: // PKCS7Pad pads data using PKCS7.
  // See hhttp://tools.ietf.org/html/rfc2315.