Stoppable workers with reporting

workers.go

// Playground: http://play.golang.org/p/G9-_EtwPRg
package main

import (
	"fmt"
	"math/rand"
	"time"
)

type WorkerId int

func work(id WorkerId, stop <-chan chan<- WorkerId) {
	fmt.Printf("[work] Working on stuff in worker %d...\n", id)
	select {
	case report := <-stop:
		sleepyTime := time.Duration(500+rand.Intn(2000)) * time.Millisecond
		time.Sleep(sleepyTime)
		fmt.Printf("[work] Worker %d shut down in %s!\n", id, sleepyTime)
		report <- id
		break
	}
}

const (
	numWorkers = 10
	timeout    = 2 * time.Second
)

func main() {
	fmt.Println("[main] Starting up workers...")
	stops := make([]chan chan<- WorkerId, numWorkers)
	for i := 0; i < numWorkers; i++ {
		stop := make(chan chan<- WorkerId, 1)
		go work(WorkerId(i+1), stop)
		stops[i] = stop
	}

	time.Sleep(100 * time.Millisecond)

	fmt.Println("[main] Asking workers to shut down...")
	report := make(chan WorkerId, numWorkers)
	for i := 0; i < numWorkers; i++ {
		stops[i] <- report
	}

	fmt.Println("[main] Waiting for workers to shut down...")
	deadline := time.After(timeout)
	for i := 0; i < numWorkers; i++ {
		fmt.Printf("[main] %d worker(s) left\n", numWorkers-i)
		select {
		case id := <-report:
			fmt.Printf("[main] Worker %d reported back\n", id)
			continue
		case <-deadline:
			fmt.Println("[main] Timed out waiting for workers to shut down")
			return
		}
	}
	fmt.Println("[main] That's all folks!")
}