代码是封闭的，但是当发送多个错误时会泄漏goroutine。第一个发送errChan的worker会退出，因为主goroutine会接收到这个值。所有发送到errChan的worker会永远阻塞，因为没有goroutine接收这个值。wg.Wait(); close(errChan) goroutine也会永远阻塞，等待worker完成。
修复是双重的：使用非阻塞发送到通道，并确保errChan可以接收至少一个值。
请参阅下面的评论以了解更多详细信息：

func run() error {
    var wg sync.WaitGroup
    // Create channel with capacity one to ensure that
    // a goroutine can send to the channel before this
    // goroutine is ready to receive.
    errChan := make(chan error, 1)  // <-- note 1 here

    for i := 0; i < numWorkers; i++ {
        wg.Add(1)
        go func(num int) {
            defer wg.Done()
            doSomeWork(num, errChan)
        }(i)
    }
    go func() {
        wg.Wait()
        // All goroutines are done, but the main goroutine
        // will be waiting if there were no errors.  Close 
        // the channel so that the main goroutine receives
        // a zero error value.
        close(errChan)
    }()
    // The if statement in the original is not needed because
    // the zero value of the error interface is nil. 
    return <-errChan
}

func doSomeWork(num int, errChan chan<- error) {
    if num >= 10 {
        select {
        case errChan <- errors.New("Greater than 10"):
             // Successful send on channel
        default:
             // Channel is not ready. This implies that
             // at least one other goroutine sent an error
             // to the channel.  There's nothing for us to
             // do here. error.
        }
    }
}

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