How to close channel in golang (brief analysis of rules)

Golang (also known as Go) is an open source programming language developed by Google. It is a strongly typed programming language designed to simplify and make programs more efficient. Due to its efficiency and ease of use, Golang has gradually become a very popular programming language, especially in large-scale distributed systems.

In Golang, channel is a data type that allows communication between different coroutines. It is a very important feature because it allows coroutines to communicate in an asynchronous manner, improving the running efficiency and concurrency of the program. However, there are some issues that require special attention when using channels, including channel closing.

In Golang, channels can be closed using the built-in close() function. The main function of closing the channel is to tell the coroutines that they no longer need to send data to the channel. This is a very important operation, because if the channel is not closed, the coroutines may be blocked in the read operation of the channel, causing problems in the program.

When performing the channel closing operation, you need to follow some rules:

1. The channel cannot be closed repeatedly. Otherwise it will cause the program to crash.
2. Sending data to a closed channel will cause panic. So before we close the channel, we must make sure that all coroutines have stopped sending data to the channel.
3. Reading data from a closed channel will get a default value and will not block. This means that we can use this feature to determine whether a channel has been closed.

The following is an example showing how to properly close Golang's channel:

package main

import "fmt"

func main() {
    c := make(chan int)

    go func() {
        for i := 1; i <= 5; i++ {
            c <- i
        }
        close(c)
    }()

    for {
        v, ok := <-c
        if !ok {
            break
        }
        fmt.Println(v)
    }
}

In this example, we use a non-cache channel for communication. After starting a coroutine, we continue to send data to the channel. When the data is sent, we close the channel through the close() function. In the main thread, we continuously read data from the channel through a for loop until we find that the channel has been closed.

In short, closing the channel is a very important operation when using Golang channel. We need to make sure we close the channel at the right time and don't let the coroutine get blocked in a state where it cannot exit. Only in this way can we ensure that the program can run correctly and the concurrency performance can be maximized.

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