Time

Use time.Time for instants of time

Use time.Time when dealing with instants of time, and the methods on time.Time when comparing, adding, or subtracting time.

// BAD
func isActive(now, start, stop int) bool {
  return start <= now && now < stop
}

// GOOD
func isActive(now, start, stop time.Time) bool {
  return (start.Before(now) || start.Equal(now)) && now.Before(stop)
}

Use time.Duration for periods of time

Use time.Duration when dealing with periods of time.

// BAD
func poll(delay int) {
  for {
    // ...
    time.Sleep(time.Duration(delay) * time.Millisecond)
  }
}

poll(10) // was it seconds or milliseconds?

// GOOD
func poll(delay time.Duration) {
  for {
    // ...
    time.Sleep(delay)
  }
}

poll(10*time.Second)

Getting Next Day

Going back to the example of adding 24 hours to a time instant, the method we use to add time depends on intent. If we want the same time of the day, but on the next calendar day, we should use Time.AddDate. However, if we want an instant of time guaranteed to be 24 hours after the previous time, we should use Time.Add.

newDay := t.AddDate(0 /* years */, 0 /* months */, 1 /* days */)
maybeNewDay := t.Add(24 * time.Hour)