channels.go

package main

import (
	"fmt"
	"time"
)

func main() {
	const (
		MAX_WORKERS     = 2
		WORK_ITEM_COUNT = 3
	)

	w := []chan bool{}
	s := make(chan bool, MAX_WORKERS)
	e := make(chan error)
	c := make(chan bool)

	go func() {
		for {
			select {
			case err := <-e:
				fmt.Println("ERROR:", err)
			case <-c:
				return
			}
		}
	}()

	for i := 0; i < WORK_ITEM_COUNT; i++ {
		i := i
		n := make(chan bool)
		w = append(w, n)

		s <- true
		go func() {
			fmt.Println(i, "Start")
			if i == 1 {
				e <- fmt.Errorf("%d Oops", i)
			} else {
				time.Sleep(3 * time.Second)
			}
			fmt.Println(i, "Finish")
			<-s
			n <- true
		}()
	}

	for _, n := range w {
		<-n
	}
	c <- true

	fmt.Println("Done")
}