context timeout routine泄漏问题

go-context-cancel.go

package main

import (
	"fmt"
	"golang.org/x/net/context"
	"log"
	"math/rand"
	"runtime"
	"time"
)

func job() error {
	ctx, cancel := context.WithTimeout(context.Background(), time.Second)
	defer cancel()

	done := make(chan struct{})
	defer close(done)

	go func() {
		time.Sleep(time.Second * time.Duration(rand.Intn(5)))

		//if _, ok := <- done; ok {
		//	done <- struct{}{}
		//}
		select {
		case <-ctx.Done():
			log.Println("receive cancel signal ready to break")
			return
		default:
			done <- struct{}{}
		}
	}()

	select {
	case <-done:
		return nil
	case <-ctx.Done():
		return ctx.Err()
	}
}
func main() {
	for i := 0; i < 50; i++ {
		go func() {
			fmt.Println(job())
		}()
	}

	for true {
		time.Sleep(time.Second)
		fmt.Println("current routine num:", runtime.NumGoroutine())
	}
}