code: func TimeAtOrIn(from, at time.Time, in time.Duration) time.Time {
  	if in == 0 {
  		return at
  	}
  	return from.Add(in)
  }
docs: // TimeAtOrIn returns either "at", or the "in" duration added to the current
  // time. TimeAtOrIn prefers to add a duration rather than return the "at"
  // parameter.