使用channel控制goroutine执行顺序

有个缺点: 控制n个goroutine就需要创建n个chan

package controllgoroutine

import (
	"fmt"
	"sync"
)

var wg sync.WaitGroup

func ControlGoroutineExeSequence() {
	ch1 := make(chan struct{}, 1)
	ch2 := make(chan struct{}, 1)
	ch3 := make(chan struct{}, 1)
	ch1 <- struct{}{} // 必须要有容量为1的buf,否则这里就会阻塞
	wg.Add(3)
	go func(gid int, in, out chan struct{}) {
		select {
		case <-in:
			fmt.Printf("goroutune: %v\n", gid)
			out <- struct{}{} // 打印完就传信号给另一个chan执行!
		}
		wg.Done()
	}(1, ch1, ch2)
	go func(gid int, in, out chan struct{}) {
		select {
		case <-in:
			fmt.Printf("goroutune: %v\n", gid)
			out <- struct{}{}
		}
		wg.Done()
	}(2, ch2, ch3)
	go func(gid int, in, out chan struct{}) {
		select {
		case <-in:
			fmt.Printf("goroutune: %v\n", gid)
			out <- struct{}{}
		}
		wg.Done()
	}(3, ch3, ch1)
	wg.Wait()
}