How to properly close a program in Golang

Go language (Golang) is an excellent high-level programming language developed by Google. It has the advantages of efficiency, reliability, simplicity, etc., making more and more people choose to use it to write code. However, you may encounter some problems when using Golang, such as how to close the program. This article will introduce how to shut down the program correctly in Golang.

1. What is closure?

Close means that after the program completes the task, it terminates its own operation in time to release the resources occupied during runtime. In Golang, we generally use os.Signal to close.

2. How to close?

In Golang, we can use os.Signal to shut down, which is a signal used to control the process. Let's introduce several ways to use os.Signal to close the program.

1. Use the Ctrl C shortcut key

When running a program in the terminal, we can use the Ctrl C shortcut key to close the program. When you press Ctrl C, the system will send an interrupt signal (SIGINT) to the program, and the program will stop running after receiving this signal. Here is an example:

package main

import (
    "fmt"
    "os"
    "os/signal"
    "syscall"
)

func main() {
    c := make(chan os.Signal, 1)
    signal.Notify(c, os.Interrupt, syscall.SIGTERM)
    <-c
    fmt.Println("程序已关闭")
}

In the above example, we used signal.Notify to listen for operating system signals received by the program. When the program receives the os.Interrupt or syscall.SIGTERM signal, it will stop running.

2. Use the kill command

In addition to using the Ctrl C shortcut key, we can also use the kill command to close the program. The kill command can send different signals to the process. You can use the kill -l command to view all signals. In Golang, we can use the syscall.SIGTERM signal to shut down. Here is an example:

package main

import (
    "fmt"
    "os"
    "syscall"
)

func main() {
    pid := os.Getpid()
    fmt.Println("PID:", pid)

    pgid, err := syscall.Getpgid(pid)
    if err != nil {
        panic(err)
    }
    fmt.Println("PGID:", pgid)

    syscall.Kill(-pgid, syscall.SIGTERM)

    fmt.Println("程序已关闭")
}

In the above example, we used os.Getpid and syscall.Getpgid to get the ID of the current process and group. Then use syscall.Kill to send the SIGTERM signal to the process group, and finally the program will shut down.

3. How to handle the program shutdown event?

In Golang, when the program receives a shutdown signal, we can do some cleanup work, such as saving some data, stopping background tasks, closing database connections, etc. We can use channels to implement this function. The specific implementation is as follows:

package main

import (
    "fmt"
    "os"
    "os/signal"
    "syscall"
)

func cleanup() {
    // 做一些清理工作
    fmt.Println("清理完毕")
}

func main() {
    c := make(chan os.Signal, 1)
    signal.Notify(c, os.Interrupt, syscall.SIGTERM)

    go func() {
        <-c
        cleanup()
        os.Exit(0)
    }()

    // 程序正常运行
    fmt.Println("程序正常运行...")
    for {
        // 这里可以写一些业务代码
    }
}

In the above example, we use a function called cleanup to perform cleaning work. In the main function, we use goroutine to listen for signals received by the program. When the program receives the signal, it will call the cleanup function to clean up, and finally use os.Exit(0) to exit the program. When using this method, we need to store some important data, resources, etc. on the disk or database to avoid losing it when the program is closed.

4. Summary

In this article, we introduced how to correctly close the program in Golang, using os.Signal, kill command and channel (Channel) respectively. When the program receives the shutdown signal, we need to do some cleanup work, such as saving some data, stopping background tasks, closing the database connection, etc. A good shutdown mechanism can avoid unexpected program exit and resource leakage, and improve the stability and reliability of the program.

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