Go Channels Waiting for work to finish


Example

A common technique for using channels is to create some number of workers (or consumers) to read from the channel. Using a sync.WaitGroup is an easy way to wait for those workers to finish running.

package main

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

func main() {
    numPiecesOfWork := 20
    numWorkers := 5

    workCh := make(chan int)
    wg := &sync.WaitGroup{}

    // Start workers
    wg.Add(numWorkers)
    for i := 0; i < numWorkers; i++ {
        go worker(workCh, wg)
    }

    // Send work
    for i := 0; i < numPiecesOfWork; i++ {
        work := i % 10 // invent some work
        workCh <- work
    }

    // Tell workers that no more work is coming
    close(workCh)

    // Wait for workers to finish
    wg.Wait()

    fmt.Println("done")
}

func worker(workCh <-chan int, wg *sync.WaitGroup) {
    defer wg.Done() // will call wg.Done() right before returning

    for work := range workCh { // will wait for work until workCh is closed
        doWork(work)
    }
}

func doWork(work int) {
    time.Sleep(time.Duration(work) * time.Millisecond)
    fmt.Println("slept for", work, "milliseconds")
}