golang 學習之等待goroutine执行完成

package main

import (

"fmt"

"sync"

"time"

"sync/atomic"

)

func main() {

wg := sync.WaitGroup{}

var i int32

for i =0; i <20; i++ {

wg.Add(1)

tmp := atomic.LoadInt32(&i)

go func() {

defer wg.Done()

fmt.Println("i :", tmp)

}()

}

wg.Wait()

var wg1 sync.WaitGroup

for i :=0; i <5; i++ {

wg1.Add(1)

go func(n int) {

defer wg1.Done()

EchoNumber(n)

}(i)

}

wg1.Wait()

}

func EchoNumber(i int){

time.Sleep(10)

fmt.Println(i)

}