Add(1)Done()Wait()

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package main

import (
    "fmt"
    "sync"
    "time"
)

func main() {
    wg := sync.WaitGroup{}
    wg.Add(1)

    done := make(chan struct{})

    go func() {
        wg.Wait()
        done <- struct{}{}
    }()

    go func() {
        time.Sleep(5 * time.Second)
        wg.Done()
    }()

    timeout := time.Duration(10) * time.Second
    fmt.Printf("Wait for waitgroup (up to %s)\n", timeout)

    select {
    case <-done:
        fmt.Printf("Wait group finished\n")
    case <-time.After(timeout):
        fmt.Printf("Timed out waiting for wait group\n")
    }

    fmt.Printf("Free at last\n")
}

未超时,输出:

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Wait for waitgroup (up to 10s)
Wait group finished
Free at last

修改 Sleep 时间

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go func() {
    time.Sleep(15 * time.Second)
    wg.Done()
}()

超时输出:

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Wait for waitgroup (up to 10s)
Timed out waiting for wait group
Free at last

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