code: func (c *CustomerIO) TrackAnonymous(eventName string, data map[string]interface{}) error {
  	body := map[string]interface{}{"name": eventName, "data": data}
  	j, err := json.Marshal(body)
  
  	if err != nil {
  		return err
  	}
  
  	status, responseBody, err := c.request("POST", c.anonURL(), j)
  
  	if err != nil {
  		return err
  	} else if status != 200 {
  		return &CustomerIOError{status, c.anonURL(), responseBody}
  	}
  
  	return nil
  }
docs: // TrackAnonymous sends a single event to Customer.io for the anonymous user