Go 中的扇出-扇宁

// produce is simulating our single input as a channel
func produce() chan int {
    ch := make(chan int)
    go func() {
        for i := 0; i < 10; i++ {
            ch <- rand.Intn(50)
        }
        fmt.Printf("producer done\n")
        close(ch) // this is important!!!
    }()
    return ch
}

func worker(id int, jobs chan int, out chan OddEven, wg *sync.WaitGroup) {
    for value := range jobs {
        odd := "even"
        if (value & 1) == 1 {
            odd = "odd"
        }
        out <- OddEven{
            Number:  value,
            OddEven: odd,
        }
    }
    close(out) // remember this
    wg.Done()
}

// OddEven struct will be the result of the work done by each fanout thread
// and be the fanin data
type OddEven struct {
    Number  int
    OddEven string
}

func fanin(inputs []chan OddEven) chan OddEven {
    output := make(chan OddEven)

    var wg sync.WaitGroup
    for i, input := range inputs {
        wg.Add(1)
                // explicit params to capture loop vars
        go func(id int, input chan OddEven, output chan OddEven, wg *sync.WaitGroup) {
            for value := range input {
                output <- value
            }
            fmt.Printf("done merging source %d\n", id)
            wg.Done()
        }(i, input, output, &wg)
    }
    go func() {
        wg.Wait()
        close(output) // this is important!!!
    }()

    return output
}

func main() {
    // simulate the input data stream
    inputCh := produce()

    numWorkers := 3
    // fan-out to send data items to workers as individual jobs
    var wg sync.WaitGroup
    workerResults := make([]chan OddEven, numWorkers)
    for i := 0; i < numWorkers; i++ {
        wg.Add(1)
        workerResults[i] = make(chan OddEven)
        go worker(i, inputCh, workerResults[i], &wg)
    }
    go func() {
        wg.Wait()
    }()

    // fan-in the results
    results := fanin(workerResults)

    done := make(chan bool)
    go func() {
        for value := range results {
            fmt.Printf("got %d is %s\n", value.Number, value.OddEven)
        }
        close(done)
    }()
    <-done
    fmt.Println("done")
}