Go by Example: Timers

We often want to execute Go code at some point in the future, or repeatedly at some interval. Go’s built-in timer and ticker features make both of these tasks easy. We’ll look first at timers and then at tickers.

package main
import "time"
import "fmt"
func main() {

Timers represent a single event in the future. You tell the timer how long you want to wait, and it provides a channel that will be notified at that time. This timer will wait 2 seconds.

	timer1 := time.NewTimer(time.Second * 2)

The <-timer1.C blocks on the timer’s channel C until it sends a value indicating that the timer expired.

	<-timer1.C
	fmt.Println("Timer 1 expired")

If you just wanted to wait, you could have used time.Sleep. One reason a timer may be useful is that you can cancel the timer before it expires. Here’s an example of that.

	timer2 := time.NewTimer(time.Second)
	go func() {
		<-timer2.C
		fmt.Println("Timer 2 expired")
	}()
	stop2 := timer2.Stop()
	if stop2 {
		fmt.Println("Timer 2 stopped")
	}
}

The first timer will expire ~2s after we start the program, but the second should be stopped before it has a chance to expire.

$ go run timers.go
Timer 1 expired
Timer 2 stopped

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