Golang解决fatal error: all goroutines are asleep - deadlock!

今天进行一个协程操作demo时总是报错

//workerpool.go
package main

import (
	"fmt"
	"time"
)

//工作线程
func workerPool(jobs <-chan int, results chan<- int) {
	for j := range jobs {
		fmt.Println("start job", j)
		time.Sleep(time.Second) //模拟耗时工作
		fmt.Println("finish job", j)
		results <- j
	}
}

func main() {
	const numJobs = 5
	jobs := make(chan int, numJobs)    //
	results := make(chan int, numJobs) //

	go workerPool(jobs, results)

	for i := 1; i <= numJobs; i++ {
		jobs <- i
	}
        close(jobs)
        for r := range results {
		fmt.Println("results :", r)
	}
}

go run workerpool.go 报错

start job 1
finish job 1
start job 2
results : 1
finish job 2
start job 3
results : 2
finish job 3
start job 4
results : 3
finish job 4
start job 5
results : 4
finish job 5
fatal error: all goroutines are asleep - deadlock!
results : 5

goroutine 1 [chan receive]:
main.main()
	workerpool.go:30 +0x19d

asleep就是说协程都在睡觉没做事

问题应该出在遍历jobs上, jobs遍历完没数据可操作了，引发 asleep - deadlock 报错

改进方法：

1、是无限循环输入数据到jobs

2、用waitGroup

方法1的无限循环输入数据就不做介绍了，比较简单

下面展示一下方法2使用waitGroup的方式

package main

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

var wg sync.WaitGroup

//工作线程
func workerPool(jobs <-chan int, results chan<- int) {
	for j := range jobs {
		fmt.Println("start job", j)
		time.Sleep(time.Second)
		fmt.Println("finish job", j)
		results <- j
	}
}

func init() {
	wg = sync.WaitGroup{}
}

func main() {
	const numJobs = 5
	jobs := make(chan int)    //
	results := make(chan int) //

	go workerPool(jobs, results)
	go func() {
		for r := range results {
			fmt.Println("results :", r)
			wg.Done()//接收到数据,表示完成了一份工作
		}
	}()

	for i := 1; i <= numJobs; i++ {
		wg.Add(1)//标记开始一份工作
		jobs <- i
	}

	wg.Wait()

}

正常运行结果如下：

start job 1

finish job 1

start job 2

results : 1

finish job 2

start job 3

results : 2

finish job 3

start job 4

results : 3

finish job 4

start job 5

results : 4

finish job 5

results : 5

Process finished with exit code 0