Golang coroutine closes

In Go language, coroutine is an important concurrent programming mechanism. It allows multiple tasks to be executed in parallel, thereby improving program efficiency. The coroutine implementation of the Go language is based on lightweight threads (or user-level threads), so the cost of creating and destroying coroutines is very small. However, in actual development, we sometimes need to close the running coroutine, and in this case we need to use some special means to achieve this. This article introduces some methods and techniques about golang coroutine shutdown.

1. The essence of coroutines

Before understanding how to close coroutines, we need to first understand the nature of coroutines. A coroutine is essentially an independent thread of execution that executes in parallel with the main thread. Each coroutine has its own stack and local variables, but they share the same process and global variables. The creation and destruction of coroutines only requires a few instructions, so it is very efficient.

2. How to close the coroutine

1. Close the coroutine through context.Context

In Go language, you can use context.Context to Control the execution of coroutines. A Context with cancellation function can be created through the context.WithCancel function. When the Cancel function of the Context is called, all coroutines that depend on the Context will be closed. The following is a simple sample code:

func main() {
    ctx, cancel := context.WithCancel(context.Background())
    go func() {
        for {
            select {
            case <-ctx.Done():
                log.Println("The goroutine is stopped.")
                return
            default:
                // do something
            }
        }
    }()
    time.Sleep(time.Second)
    cancel()
    time.Sleep(time.Second)
}

In this example, we create a Context with cancellation function and create a coroutine in which certain operations are continuously performed until Context is cancelled. Wait for one second in the main thread and then call the Cancel function of Context to close the coroutine.

2. Close the coroutine through channel

In addition to using context.Context to control the running of the coroutine, you can also use channel to implement it. Normally, we can create a bool type channel to pass the signal whether to close the coroutine. When the main thread calls the close function of the channel, all coroutines reading the channel will receive a zero-value signal and exit. The following is a sample code:

func main() {
    stopCh := make(chan bool)
    go func() {
        for {
            select {
            case <-stopCh:
                log.Println("The goroutine is stopped.")
                return
            default:
                // do something
            }
        }
    }()
    time.Sleep(time.Second)
    close(stopCh)
    time.Sleep(time.Second)
}

In this example, we create a bool type channel to pass the signal whether to close the coroutine. In the coroutine, use the select statement to continuously check whether the channel is closed, and if it is closed, exit. Wait for one second in the main thread and then call the close function of the channel to close the coroutine.

3. Close the coroutine through sync.WaitGroup

In addition to using context.Context and channel to control the running of the coroutine, you can also use sync.WaitGroup to implement it. WaitGroup is a counter that can be used to wait for the end of a group of coroutines. Specifically, when the coroutine is created, the counter of the WaitGroup is incremented by one, and after the coroutine is executed, the counter is decremented by one. In the main thread, call the Wait function of WaitGroup to wait for all coroutines to finish executing and then close the program. Here is a sample code:

func main() {
    var wg sync.WaitGroup
    wg.Add(1)
    go func() {
        defer wg.Done()
        for {
            // do something
        }
    }()
    time.Sleep(time.Second)
    wg.Done()
    wg.Wait()
}

In this example, we create a WaitGroup and increment the counter by one. In the coroutine, perform certain operations, wait for the end of the coroutine, and call the Done function of WaitGroup to decrement the counter by one. Wait for one second in the main thread before calling the WaitGroup's Done function, and then call the Wait function to wait for all coroutines to finish executing and then close the program.

3. Summary

The coroutine of Go language is a very powerful concurrent programming mechanism and is widely used in development. However, in actual development, sometimes we need to close the running coroutine, and in this case we need to use some special means to achieve this. This article introduces some methods and techniques for closing golang coroutines. I hope it will be helpful to everyone.

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