golang timer close

Golang is a modern programming language for developing high performance. Its timer is a very practical function that can perform some tasks within a predetermined time interval. However, sometimes we need to manually turn off a timer to avoid unnecessary waste of resources and program crashes. This article will explore how to turn off a timer in Golang.

1. Basic principles of timers

In Golang, we can use the timer function in the time package. The basic code to create a timer is as follows:

timer := time.NewTimer(time.Second * 5)

This line of code will create a timer instance that will fire after 5 seconds. We can perform some tasks after the timer is triggered, for example:

<- timer.C
fmt.Println("定时器已触发！")

When the timer expires, it will send a time to channel C. We can read this time from the channel and execute the corresponding task. The above code will output a line of text proving that the timer has fired.

2. Turn off the timer

We have learned how to create a timer. Now, we need to learn how to turn it off. In Golang, we can use the Stop() method to manually close a timer. The function of this method is simple: it stops the execution of the timer and makes channel C unable to receive any more messages.

For example, the following code will create a 5-second timer and manually close it after 3 seconds:

timer := time.NewTimer(time.Second * 5)
go func() {
    time.Sleep(time.Second * 3)
    timer.Stop()
}()
<- timer.C
fmt.Println("定时器已触发！")

In this example, after the timer is created, A new coroutine was started and closed manually after 3 seconds. Because this timer has been closed, channel C will no longer receive any messages, so no tasks will be triggered.

3. Precautions for turning off the timer

Although the process of turning off the timer seems simple, there are actually some things that need to be paid attention to. In this section, we'll explore some common problems and solutions regarding timer shutdown.

1. Timer closing may block the program

In the previous example, we demonstrated how to close a timer in a coroutine. This approach is usually the best approach as it avoids blocking the main program. But what happens if we turn off a timer in the main program?

For example, the following code creates a 5-second timer and attempts to close it after 3 seconds:

timer := time.NewTimer(time.Second * 5)
time.Sleep(time.Second * 3)
timer.Stop()
<- timer.C
fmt.Println("定时器已触发！")

In this example, we use time.Sleep( ) function to pause the main program for 3 seconds. We then try to turn off the timer and wait for it to execute. However, this program will actually be blocked and wait for the timer execution result.

This is because when the timer is turned off, it will still send a message to channel C. If we wait on channel C, the program will be blocked. In order to avoid this situation, we can use the Select statement to wait for the execution result of the timer.

The following code demonstrates how to use the Select statement to wait for the execution result of the timer:

timer := time.NewTimer(time.Second * 5)
time.Sleep(time.Second * 3)
if !timer.Stop() {
    <- timer.C
}
fmt.Println("定时器已关闭！")

In this example, we use the timer.Stop() function to try to turn off the timer. If this function returns false, it means that the timer has not yet completed execution. At this point, we need to read a message from channel C to ensure that our program will not be blocked. Otherwise, we directly output a text indicating that the timer has been turned off.

2. The execution of the timer may be uncertain

When we use the Select statement to wait for the execution result of the timer, we may find that the execution result of the timer is not sure. In other words, it is possible that the channel C message we received is not a timer trigger message. This is because we used the Stop() function to manually close the timer, and this operation may have interfered with the normal execution of the timer.

For example, the code below creates a 5 second timer and attempts to close it after 2 seconds. Then, we use the Select statement to wait for the execution result of the timer:

timer := time.NewTimer(time.Second * 5)
time.Sleep(time.Second * 2)
timer.Stop()
select {
    case <- timer.C:
        fmt.Println("定时器已触发！")
    default:
        fmt.Println("定时器已关闭！")
}

In this example, we use the Select statement to wait for the execution result of the timer. However, since we manually turned off the timer after 2 seconds, the final output may be "Timer has been turned off!" instead of "Timer has triggered!". In this case, the execution result of the timer is uncertain.

In order to avoid this situation, we can record a timestamp when the timer is created to ensure that the execution result of the timer is correct. For example:

timer := time.NewTimer(time.Second * 5)
start := time.Now()
time.Sleep(time.Second * 2)
timer.Stop()
if time.Since(start) < (time.Second * 5) {
    select {
        case <- timer.C:
            fmt.Println("定时器已触发！")
        default:
            fmt.Println("定时器已关闭！")
    }
}

In this example, we recorded the current timestamp when the timer was created. When we try to turn off the timer, we check the difference between the current time and the time interval scheduled by the timer. If the gap is less than 5 seconds, it means that the timer has not been executed yet. We can wait for the execution result of the timer through the Select statement. Otherwise, we directly output a text message indicating that the timer has been turned off.

4. Summary

The timer in Golang is a very practical function that can help us automatically perform some repetitive tasks. However, in order to avoid wasting resources and program crashes, we need to learn how to manually turn off a timer. In this article, we introduced how to use the Stop() function to turn off a timer and discussed some possible problems and solutions. After learning these skills, we can better use Golang's timer function to bring better performance and efficiency to our programs.

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