M Receivers 1 Sender

• Fan-Out
• 多個接收端, 1個Sender.
• 當不想發送資料時, 直接在Sender關閉 dataCh channel.

Exercises

https://go.dev/play/p/3srmQv9drAz

package main

import (
    "time"
    "math/rand"
    "sync"
    "log"
)

func main() {
    rand.Seed(time.Now().UnixNano())
    log.SetFlags(0)

    // ...
    const Max = 100000
    const NumReceivers = 100

    wgReceivers := sync.WaitGroup{}
    wgReceivers.Add(NumReceivers)

    // ...
    dataCh := make(chan int)

    // the sender
    go func() {
        for {
            if value := rand.Intn(Max); value == 0 {
                // The only sender can close the
                // channel at any time safely.
                close(dataCh) // <-- Here
                return
            } else {
                dataCh <- value
            }
        }
    }()

    // receivers
    for i := 0; i < NumReceivers; i++ {
        go func() {
            defer wgReceivers.Done()

            // Receive values until dataCh is
            // closed and the value buffer queue
            // of dataCh becomes empty.
            for value := range dataCh {
                log.Println(value)
            }
        }()
    }

    wgReceivers.Wait()
}