signalend.go

package main

import (
	"fmt"
	"math/rand"
	"os"
	"os/signal"
	"sync"
	"time"
)

const maxWorkers = 3

func main() {
	deliveries := make(chan int)
	sending := make(chan bool)

	var listeners [3]chan bool
	var done sync.WaitGroup

	// Spin up some workers
	for i := 0; i < maxWorkers; i++ {
		done.Add(1)
		cancel := make(chan bool)
		listeners[i] = cancel
		go worker(i+1, deliveries, cancel, &done)
	}

	go func() {
	Loop:
		for {
			select {
			case <-sending:
				break Loop
			default:
				deliveries <- rand.Intn(10)
				time.Sleep(time.Second * 1)
			}
		}
	}()

	c := make(chan os.Signal, 1)
	signal.Notify(c, os.Interrupt)
	fmt.Println("Signal received")
	<-c

	// stop sending
	fmt.Println("Stop sending")
	sending <- false

	// stop consuming
	fmt.Println("Stop workers")
	for _, l := range listeners {
		l <- true
	}

	// wait for each worker to signal done
	fmt.Println("Waiting for workers to complete tasks...")
	done.Wait()
	fmt.Println("All done, exiting")
}

func worker(id int, deliveries chan int, cancel chan bool, done *sync.WaitGroup) {
Loop:
	for {
		select {
		case d := <-deliveries:
			process(id, d)
		case <-cancel:
			break Loop
		}
	}

	fmt.Printf("Worker %d has finished all tasks, signalling compete...", id)
	done.Done()
}

func process(id, d int) {
	fmt.Printf("Worker %d processing task: %d\n", id, d)
	time.Sleep(time.Second * time.Duration(d))
	fmt.Printf("Worker %d completed task: %d\n", id, d)
}