```
package main
import (
"fmt"
"math/rand"
"sync"
"time"
)
var wg sync.WaitGroup
//计算一个64位随机数的各位的和
func randNumber(x int64) int64 {
var sum int64 = 0
for x > 0 {
a := x % 10
x = x / 10
sum += a
}
return sum
}
func main() {
wg.Add(25)
var jobChan = make(chan int64, 10)
var resultChan = make(chan int64, 10)
go func(jobChan chan<- int64, ) {
defer wg.Done()
for i:=0;i<1000;i++{
rand.Seed(time.Now().UnixNano())
jobChan <- rand.Int63n(100)
}
}(jobChan)
for i:=0;i<24;i++{
go func(jobChan <-chan int64, resultChan chan<- int64, ) {
defer wg.Done()
for num:= range jobChan{
resultChan <- randNumber(num)
}
}(jobChan, resultChan)
}
for i:= range resultChan{
fmt.Println(i)
}
wg.Wait()
}
```
发生错误:fatal error: all goroutines are asleep - deadlock!
请问为什么会发生死锁的问题
* [Go 语言中通道死锁经典错误案例详解][1]
[1]: https://studygolang.com/articles/29077#reply0
#2
更多评论
为什么会发生死锁的问题?
* jobChan在数据生产结束之后没有关闭
* resultChan 没有额外再起协程去消费
以上两点造成:
* 当jobChan没有新数据往里面放的时候,**for i := 0; i < 24; i++** 这一行起的24个协程一直在等待新数据到来,一直在***for num := range jobChan **处等待,阻塞了
* 主函数里面的**for i:= range resultChan** 也一直在等待resultChan的数据,阻塞了。
* 到这里,所有的协程都阻塞,然后就出现了 **fatal error: all goroutines are asleep - deadlock! **..
要想解决这个问题,可以按照以下修改
```golang
package main
import (
"fmt"
"math/rand"
"sync"
"time"
)
var wg sync.WaitGroup
//计算一个64位随机数的各位的和
func randNumber(x int64) int64 {
var sum int64 = 0
for x > 0 {
a := x % 10
x = x / 10
sum += a
}
return sum
}
func main() {
wg.Add(25)
var jobChan = make(chan int64, 10)
var resultChan = make(chan int64, 10)
go func(jobChan chan<- int64) {
defer wg.Done()
for i := 0; i < 1000; i++ {
rand.Seed(time.Now().UnixNano())
jobChan <- rand.Int63n(100)
}
// **关闭channel**
close(jobChan)
}(jobChan)
for i := 0; i < 24; i++ {
go func(jobChan <-chan int64, resultChan chan<- int64) {
defer wg.Done()
for num := range jobChan {
resultChan <- randNumber(num)
}
}(jobChan, resultChan)
}
// **再起一个协程去消费channel**
go func() {
for i := range resultChan {
fmt.Printf("%d\n", i)
}
}()
time.Sleep(10 * time.Second)
fmt.Print("\n\nend...\n\n")
wg.Wait()
}
```
#1
for num:= range jobChan{
resultChan <- randNumber(num)
}
这个循环退出不了
#3