golang range channel死锁问题

今天采用WaitGroup来实现协程，发现range chanel会死锁，代码如下：package main

import "sync"
import "fmt"

func main() {
   var wg sync.WaitGroup
   wg.Add(3)
   resultChannel := make(chan int, 3)
   routineFunc := func(i int) {
      defer wg.Done()
      resultChannel <- i
      fmt.Println("push to channel,", i)
   }

   for i := range []int{1, 2, 3} {
      go routineFunc(i)
   }
   wg.Wait()

   fmt.Println("wg.wait")

   for res := range resultChannel {
      fmt.Println("got from channel,", res)
   }
}

运行时会出现错误：

　　push to channel, 0
　　push to channel, 1
　　push to channel, 2
　　wg.wait
　　got from channel, 0
　　got from channel, 1
　　got from channel, 2
　　fatal error: all goroutines are asleep - deadlock!

 

原因是：for range是阻塞式读取channel，只有channel close之后才会结束，否则会一直读取，通道里没有值了，还继续读取就会阻塞，程序就会报死锁。

改成如下即可：

 

package main

import "sync"
import "fmt"

func main() {
   var wg sync.WaitGroup
   wg.Add(3)
   resultChannel := make(chan int, 3)
   routineFunc := func(i int) {
      defer wg.Done()
      resultChannel <- i
      fmt.Println("push to channel,", i)
   }

   for i := range []int{1, 2, 3} {
      go routineFunc(i)
   }
   wg.Wait()
   close(resultChannel)

   fmt.Println("wg.wait")

   for res := range resultChannel {
      fmt.Println("got from channel,", res)
   }
}