这是我的 Golang 程序，我正在使用它只是为了让我的概念正确。
当我运行程序时，它陷入僵局，我不明白为什么？
请有人指出出了什么问题吗？
package main
import (
"fmt"
"sync"
)
var wg sync.WaitGroup
func main() {
numOfGoRoutines := 10
wg.Add(numOfGoRoutines)
ch := make(chan int, numOfGoRoutines)
for i := 0; i < numOfGoRoutines; i++ {
a := i
go sqr(ch, a, wg)
}
wg.Wait()
fmt.Println("After WAIT")
close(ch)
var res int
for i := range ch {
res += i
}
ch = nil
fmt.Println("result = ", res)
}
func sqr(ch chan int, val int, wg sync.WaitGroup) {
fmt.Println("go - ", val)
s := val * val
ch <- s
wg.Done()
}
输出是：
warning: GOPATH set to GOROOT (C:\\Go) has no effect
go - 9
go - 0
go - 1
go - 2
go - 3
go - 4
go - 5
go - 6
go - 7
go - 8
fatal error: all goroutines are asleep - deadlock!
goroutine 1 [semacquire]:
sync.runtime_Semacquire(0x5bcabc)
C:/Go/src/runtime/sema.go:47 +0x2d
sync.(*WaitGroup).Wait(0x5bcab0)
C:/Go/src/sync/waitgroup.go:127 +0xbb
main.main()
C:/demo/go-work/main.go:20 +0xdf
exit status 2
问题是你正在传递一个副本sync.WaitGroup到 goroutine，而不是引用（即指针）：
package main
import (
"fmt"
"sync"
)
var wg sync.WaitGroup
func main() {
numOfGoRoutines := 10
wg.Add(numOfGoRoutines)
ch := make(chan int, numOfGoRoutines)
for i := 0; i < numOfGoRoutines; i++ {
a := i
go sqr(ch, a, &wg)
}
wg.Wait()
fmt.Println("After WAIT")
close(ch)
var res int
for i := range ch {
res += i
}
ch = nil
fmt.Println("result = ", res)
}
func sqr(ch chan int, val int, wg *sync.WaitGroup) {
fmt.Println("go - ", val)
s := val * val
ch <- s
wg.Done()
}
另外，由于wg是一个全局变量，您可以完全删除该参数：
package main
import (
"fmt"
"sync"
)
var wg sync.WaitGroup
func main() {
numOfGoRoutines := 10
wg.Add(numOfGoRoutines)
ch := make(chan int, numOfGoRoutines)
for i := 0; i < numOfGoRoutines; i++ {
a := i
go sqr(ch, a)
}
wg.Wait()
fmt.Println("After WAIT")
close(ch)
var res int
for i := range ch {
res += i
}
ch = nil
fmt.Println("result = ", res)
}
func sqr(ch chan int, val int) {
fmt.Println("go - ", val)
s := val * val
ch <- s
wg.Done()
}
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