producer_consumer.go

package main

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

type Load struct {
	val int
	eod bool
}

type Worker struct {
	name  string
	speed int
	done  int
}

func (w *Worker) Work(c chan Load, finished chan *Worker) {
	for {
		v := <-c
		if v.eod {
			fmt.Printf("finishing worker %v\n", w.name)
			fmt.Printf("worker %v is done at %d\n", w.name, w.done)
			finished <- w
		} else {
			fmt.Printf("worker %v got %d\n", w.name, v.val)
		}
		for i := 0; i < 10/w.speed; i++ {
			time.Sleep(time.Millisecond * 1000)
		}
		fmt.Printf("worker %v processed %d\n", w.name, v.val)
		w.done++
	}
}

func main() {
	c := make(chan Load)
	finished := make(chan *Worker)
	workers := []*Worker{
		{name: "A", speed: 8},
		{name: "B", speed: 2},
		{name: "C", speed: 3},
	}

	// launch workers
	for _, w := range workers {
		go w.Work(c, finished)
	}

	// send loads
	for i := 0; i < 30; i++ {
		c <- Load{val: i, eod: false}
		time.Sleep(time.Millisecond * time.Duration(rand.Int31n(2000)))
	}

	// send sentinels
	for _, _ = range workers {
		c <- Load{val: -1, eod: true}
	}

	remaining := make(map[*Worker]bool)
	for _, w := range workers {
		remaining[w] = false
	}
	for len(remaining) > 0 {
		w := <-finished
		delete(remaining, w)
	}
}