cond_var.go

package main

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

var tasks []int
var wg sync.WaitGroup
var mu sync.Mutex
var cond = sync.NewCond(&mu)
var done = make(chan bool)

func consumer(id int) {
	for {
		cond.L.Lock()
		for len(tasks) == 0 {
			cond.Wait()

			select {
			case <-done:
				fmt.Println("Consumer", id, "got signal")

				cond.L.Unlock()
				return
			default:
			}
		}

		task := tasks[0]
		tasks = tasks[1:]
		cond.L.Unlock()

		fmt.Println("Consuming value", task, "from consumer", id)
	}
}

func producer() {
	i := 0

	for {
		select {
		case <-done:
			fmt.Println("Producer got signal")
			return
		default:
		}

		cond.L.Lock()
		fmt.Println("Producing value", i)
		tasks = append(tasks, i)
		cond.Signal()
		cond.L.Unlock()

		i++
		<-time.After(500 * time.Millisecond)
	}
}

func main() {
	n := 5
	wg.Add(n + 1)

	for i := 0; i < n; i++ {
		go func(i int) {
			consumer(i)
			wg.Done()
		}(i)
	}

	go func() {
		producer()
		wg.Done()
	}()

	<-time.After(10 * time.Second)
	close(done)
	cond.Broadcast()
	fmt.Println("Signaled done")
	wg.Wait()
}