How to properly close channels in golang

Golang is a programming language that has become increasingly popular among developers in recent years. It provides many convenient features, one of which is Channel.

Channel is a mechanism used for communication between Goroutines in Golang. The advantage of channels is that they can guarantee the atomicity of data exchange and can achieve synchronization between multiple coroutines.

When using channels, we usually encounter the situation of closing the channel. This article explains how to properly close a channel.

1. How to close the channel

Close the channel in Golang is very simple, you only need to call the function passing the channel in the program or call the Close function directly in the program. The Close function is implemented by the Go language constant "iota". Once a channel is closed, no data can be sent to it, but data can be read from a closed channel.

Sample code:

func main() {
    channel := make(chan int)
 
    go func() {
        for i := 0; i < 10; i++ {
            channel <- i
        }
        close(channel)
    }()
 
    for v := range channel {
        fmt.Println(v)
    }
}

In the above sample code, we created a channel and wrote 10 numbers in a coroutine. Finally, we use the close function to close the channel.

2. Channels are automatically closed

In Golang, channels have a very convenient feature, that is, they can be closed automatically. When the channel is not referenced by the coroutine, the channel will be automatically closed.

Sample code:

func main() {
    channel := make(chan int, 10)
 
    for i := 0; i < 10; i++ {
        channel <- i
    }
 
    go func() {
        for v := range channel {
            fmt.Println(v)
        }
    }()
 
    // 延时一段时间，等待协程执行完成
    time.Sleep(1 * time.Second)
}

In the above sample code, we create a channel with a buffer size of 10 and traverse the channel in a coroutine and output the values. Finally, we use the time library to wait for 1 second to ensure that the coroutine execution is completed. When the coroutine execution is completed, the channel will be automatically closed.

3. Avoid closing closed channels

When using channels, we need to avoid closing closed channels. If multiple coroutines try to close a channel at the same time, the program will crash.

Sample code:

func main() {
    channel := make(chan int)
 
    close(channel)
    close(channel)
}

In the above sample code, we create a channel and try to call the close function twice in the program. This will cause the program to crash.

4. Avoid sending data to closed channels

When using channels, we also need to avoid sending data to closed channels. If you send data in a closed channel, it will cause the program to crash.

Sample code:

func main() {
    channel := make(chan int)
 
    close(channel)
 
    channel <- 1
}

In the above sample code, we create a channel and call the close function in the program. Then we try to send data to the closed channel, which will cause the program to crash.

In Golang, it is very important to close the channel correctly, because closing the channel is a way to ensure the safety of the coroutine. Once a channel is closed, no data can be sent to it, but data can be read from a closed channel. When using channels, we need to avoid closing a closed channel or sending data to an already closed channel, which will cause the program to crash.

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