code: func (c chatResponseFull) getMessageTimestamp() string {
  	if len(c.Timestamp) > 0 {
  		return c.Timestamp
  	}
  	return c.MessageTimeStamp
  }
docs: // getMessageTimestamp will inspect the `chatResponseFull` to ruturn a timestamp value
  // in `chat.postMessage` its under `ts`
  // in `chat.postEphemeral` its under `message_ts`