code: func UnsafeMsgOptionEndpoint(endpoint string, update func(url.Values)) MsgOption {
  	return func(config *sendConfig) error {
  		config.endpoint = endpoint
  		update(config.values)
  		return nil
  	}
  }
docs: // UnsafeMsgOptionEndpoint deliver the message to the specified endpoint.
  // NOTE: USE AT YOUR OWN RISK: No issues relating to the use of this Option
  // will be supported by the library, it is subject to change without notice that
  // may result in compilation errors or runtime behaviour changes.