code: func DecryptString(str, key string) (string, error) {
  	k := []byte(key)
  	b64 := base64.StdEncoding
  	decodeStr, err := b64.DecodeString(str)
  	if err != nil {
  		return "", err
  	}
  	result := Decrypt([]byte(decodeStr), k)
  	return string(result), nil
  }
docs: // Decrypt the data with key.
  // data is the string to be decrypted.
  // key is the decrypted key. It is the same as the encrypt key.