多个 goroutine 并发执行时，每一个 goroutine 抢到处理器的时间点不一致，gorouine 的执行本身不能保证顺序。即代码中先写的 gorouine 并不能保证先执行

思路：使用 channel 进行通信通知，用 channel 去传递信息，从而控制并发执行顺序

package main

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

var wg sync.WaitGroup

func main() {
	ch1 := make(chan struct{}, 1)
	ch2 := make(chan struct{}, 1)
	ch3 := make(chan struct{}, 1)
	ch1 <- struct{}{}
	wg.Add(3)
	start := time.Now().Unix()
	go print("gorouine1", ch1, ch2)
	go print("gorouine2", ch2, ch3)
	go print("gorouine3", ch3, ch1)
	wg.Wait()
	end := time.Now().Unix()
	fmt.Printf("duration:%d\n", end-start)
}

func print(gorouine string, inputchan chan struct{}, outchan chan struct{}) {
	// 模拟内部操作耗时
	time.Sleep(1 * time.Second)
	select {
	case <-inputchan:
		fmt.Printf("%s\n", gorouine)
		outchan <- struct{}{}
	}
	wg.Done()
}