我正在閱讀 Go 中的并發(fā)性，并且非常接近尾聲！總的來(lái)說(shuō)，這是一本很棒的讀物。在其中一個(gè)示例中，作者描述了如何模擬請(qǐng)求復(fù)制。代碼示例如下：func main() {    doWork := func(        done <-chan interface{},        id int,        wg *sync.WaitGroup,        result chan<- int,    ) {        started := time.Now()        defer wg.Done()        // Simulate random load        simulatedLoadTime := time.Duration(1*rand.Intn(5)) * time.Second        /** use two separate select blocks because we want to send/receive two different values, the time.After (receive) and the id (send).        / if they were in the same select block, then we could only use one value at a time, the other will get lost. */        select {        // do not want to return on <-done because we still want to log the time it took        case <-done:        case <-time.After(simulatedLoadTime):        }        select {        case <-done:        case result <- id:        }        took := time.Since(started)        // Display how long handlers would have taken        if took < simulatedLoadTime {            took = simulatedLoadTime        }        fmt.Printf("%v took %v\n", id, took)    }    done := make(chan interface{})    result := make(chan int)    var wg sync.WaitGroup    wg.Add(10)    for i := 0; i < 10; i++ {        go doWork(done, i, &wg, result)    }    firstReturned := <-result    close(done)    wg.Wait()    fmt.Printf("Received an answer from #%v\n", firstReturned)}我不明白的一句話是.為什么會(huì)在這里？我們什么時(shí)候會(huì)利用從該通道返回的值。該通道是如何在選擇塊之外進(jìn)行通信的？無(wú)論出于何種原因，這條線似乎在同步結(jié)果的時(shí)間方面都是不可或缺的，因?yàn)槿绻矣胊替換它，結(jié)果就不同步了。case <-time.After(simulatedLoadTime)default: