code: func (api *Client) DeleteReminder(id string) error {
  	values := url.Values{
  		"token":    {api.token},
  		"reminder": {id},
  	}
  	response := &SlackResponse{}
  	if err := api.postMethod(context.Background(), "reminders.delete", values, response); err != nil {
  		return err
  	}
  	return response.Err()
  }
docs: // DeleteReminder deletes an existing reminder.
  //
  // See https://api.slack.com/methods/reminders.delete