code: func (api *Client) AddUserReminder(userID, text, time string) (*Reminder, error) {
  	values := url.Values{
  		"token": {api.token},
  		"text":  {text},
  		"time":  {time},
  		"user":  {userID},
  	}
  	return api.doReminder(context.Background(), "reminders.add", values)
  }
docs: // AddUserReminder adds a reminder for a user.
  //
  // See https://api.slack.com/methods/reminders.add (NOTE: the ability to set
  // reminders on a channel is currently undocumented but has been tested to
  // work)