Detect if the os has been in sleep mode by looking at the clock

monotonic.go

func hasSlept(ctx context.Context, healthCheck time.Duration, sleptTime time.Duration) <-chan struct{} {
	signalC := make(chan struct{})
	go func(chan<- struct{}) {
		tick := time.NewTicker(healthCheck)
		last := time.Now()
		for {
			select {
			case <-ctx.Done():
				return
			case <-tick.C:
				if time.Now().Round(0).Sub(last) > sleptTime {
					signalC <- struct{}{}
				}
				last = time.Now()
			}
		}
	}(signalC)
	return signalC
}

time.Now().Round(0).Sub(last) is the important line here:

From the doc:

The canonical way to strip a monotonic clock reading is to use t = t.Round(0).