我写了一个简单的 GO 程序，应该启动 3 个 GO 例程。但是，GO 例程不会启动。

请注意，情况与这篇文章中的描述者不同:

Why is my goroutine not executed?

程序应该等待 GO 例程结束它们的执行...因此，程序应该永远等待(因为例程永远不会停止)。

package main

import (
    "fmt"
    "net"
    "os"
    "time"
    "sync"
)

func main() {

    wg := sync.WaitGroup{}

    fmt.Print("Starting 3 clients\n")

    for i:=0; i<3; i++ {

        client := func(inName string) {

            fmt.Printf("Client <%s> started\n", inName)

            wg.Add(1)
            conn, err := net.Dial("tcp", ":8000")
            if err != nil {
                fmt.Printf("[%s] Error while connecting to the server: %s", inName, err.Error())
                os.Exit(1)
            }

            n := 0
            sleepDuration, _ := time.ParseDuration("2s")
            for {
                message := fmt.Sprintf("[%s] > message %d\n", inName, n)
                fmt.Printf("%s", message)
                _, err := conn.Write([]byte(message))
                if nil != err {
                    fmt.Sprintf("[%s] Error while writing data to the socket: %s", inName, err.Error())
                    os.Exit(1)
                }
                time.Sleep(sleepDuration)
                n++
            }
        }

        name := fmt.Sprintf("Client%d", i)
        fmt.Printf("Starting client <%s>...\n", name)
        go client(name)
        fmt.Print("Done\n")
    }

    wg.Wait()
}

结果:

Starting 3 clients
Starting client <Client0>...
Done
Starting client <Client1>...
Done
Starting client <Client2>...
Done

最佳答案

作为this解决方案说:

It is important that the wg.Add() happens before the go statement to prevent race conditions. The following would also be correct:

因此，您需要在 go routine 本身内部取出 wg.Add(1) 并在开始 go routines 之前调用它。此外，在函数开始时调用 defer wg.Done()，这样它会将 WaitGroup 计数器减一。看看下面的代码。

package main

import (
    "fmt"
    "net"
    "os"
    "time"
    "sync"
)

func main() {

    wg := sync.WaitGroup{}

    fmt.Print("Starting 3 clients\n")

    for i:=0; i<3; i++ {

        client := func(inName string) {

            defer wg.Done() // added this line

            fmt.Printf("Client <%s> started\n", inName)

            conn, err := net.Dial("tcp", ":8000")
            if err != nil {
                fmt.Printf("[%s] Error while connecting to the server: %s", inName, err.Error())
                os.Exit(1)
            }

            n := 0
            sleepDuration, _ := time.ParseDuration("2s")
            for {
                message := fmt.Sprintf("[%s] > message %d\n", inName, n)
                fmt.Printf("%s", message)
                _, err := conn.Write([]byte(message))
                if nil != err {
                    fmt.Sprintf("[%s] Error while writing data to the socket: %s", inName, err.Error())
                    os.Exit(1)
                }
                time.Sleep(sleepDuration)
                n++
            }
        }

        name := fmt.Sprintf("Client%d", i)
        fmt.Printf("Starting client <%s>...\n", name)
        wg.Add(1) // moved this line
        go client(name)
        fmt.Print("Done\n")
    }

    wg.Wait()
}

关于go - 为什么 GO 例程不启动？，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/49625640/