Timers {.en}

定时器 {.zh}

::: {.en} 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. :::

::: {.zh}

我们常常需要在后面一个时刻运行 Go 代码，或者在某段时间 间隔内重复运行。Go 的内置 定时器 和 打点器 特性让这 些很容易实现。我们将先学习定时器，然后再学习打点器。

:::

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

::: {.en} 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. :::

::: {.zh}

定时器表示在未来某一时刻的独立事件。你告诉定时器 需要等待的时间，然后它将提供一个用于通知的通道。 这里的定时器将等待 2 秒。

:::

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

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

::: {.zh}

<-timer1.C 在定时器的通道 C 上阻塞，直到它发送一个表示 定时器失效 的值。

:::

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

::: {.en} 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. :::

::: {.zh}

如果你需要的仅仅是单纯的等待，你需要使用 time.Sleep。 定时器是有用原因之一就是你可以在定时器失效之前，取消这个 定时器。这是一个例子

:::

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

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

::: {.zh}

第一个定时器将在程序开始后约 2s 失效，但是第二个在它 没失效之前就停止了。

:::

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