context_example.go

package main

import (
	"context"
	"log"
	"runtime"
	"time"
)

var (
	rCh     chan int
	blockCh chan struct{}
	ctx     context.Context
	cancel  context.CancelFunc
)

func init() {
	runtime.GOMAXPROCS(runtime.NumCPU())

	rCh = make(chan int, 0)

	blockCh = make(chan struct{}, 0)

	ctx, cancel = context.WithCancel(context.Background())
}

func r1(ctx context.Context) {
	for {
		select {
		case <-ctx.Done():
			log.Println("r1 exit")
			runtime.Goexit()
		case r := <-rCh:
			log.Println("r1: ", r)
		}
	}
}

func r2(ctx context.Context) {
	for {
		select {
		case <-ctx.Done():
			log.Println("r2 exit")
			runtime.Goexit()
		case r := <-rCh:
			log.Println("r2: ", r)
		}
	}
}

func sendValue(cancel context.CancelFunc) {
	i := 0
	for {
		if i > 10 {
			cancel()
		} else {
			rCh <- i
			i++
		}
		log.Println("NumGoroutine: ", runtime.NumGoroutine())
		time.Sleep(time.Duration(1) * time.Second)
	}
}

func main() {
	go r1(ctx)
	go r2(ctx)
	sendValue(cancel)
}