与Channel区别
Channel能够很好的帮助我们控制并发，但是在开发习惯上与显示的表达不太相同，所以在Go语言中可以利用sync包中的WaitGroup实现并发控制，更加直观。
基本使用示例
我们将之前的示例加以改造，引入sync.WaitGroup来实现并发控制。
- 在调用的函数中，我们需要将WaitGroup以指针方式传入，否则将造成Deadlock
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| // 主函数内
go ready(5, &wg)
// 函数
func ready(s int, wg *sync.WaitGroup)
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- 同时在函数执行完成后，调用wg.Done，我们使用defer实现
完整代码
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| package main
import (
"fmt"
"sync"
"time"
)
func ready(s int, wg *sync.WaitGroup) {
defer wg.Done()
fmt.Printf("Run func in a goroutine and wait for %v\n", s)
time.Sleep(time.Second * time.Duration(s))
fmt.Printf("Run func in a goroutine and wait for %v end\n", s)
}
func main() {
var wg sync.WaitGroup
wg.Add(1)
go ready(5, &wg)
mainWaitSec := 2
fmt.Printf("Run Main function and wait for %v\n", mainWaitSec)
time.Sleep(time.Second * time.Duration(mainWaitSec))
fmt.Printf("Run Main function and wait for %v done\n", mainWaitSec)
wg.Wait()
}
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特别提示
WaitGroup传入给函数时，需要以指针方式传递，否则会造成Deadlock
多任务示例
如果不想在函数中传递WaitGroup，也可以采用以下这种方式，通过并发匿名函数的方式，在主函数逻辑中对并发进行精准控制
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| var wg sync.WaitGroup
for i := 0; i < 5; i++ {
wg.Add(1)
waitSec := i + 1
go func() {
defer wg.Done()
ready(waitSec)
}()
}
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完整代码
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| package main
import (
"fmt"
"sync"
"time"
)
func ready(s int) {
fmt.Printf("Run func in a goroutine and wait for %v\n", s)
time.Sleep(time.Second * time.Duration(s))
fmt.Printf("Run func in a goroutine and wait for %v end\n", s)
}
func main() {
var wg sync.WaitGroup
for i := 0; i < 5; i++ {
wg.Add(1)
waitSec := i + 1
go func() {
defer wg.Done()
ready(waitSec)
}()
}
mainWaitSec := 2
fmt.Printf("Run Main function and wait for %v\n", mainWaitSec)
time.Sleep(time.Second * time.Duration(mainWaitSec))
fmt.Printf("Run Main function and wait for %v done\n", mainWaitSec)
wg.Wait()
}
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运行结果如下
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| Run Main function and wait for 2
Run func in a goroutine and wait for 2
Run func in a goroutine and wait for 4
Run func in a goroutine and wait for 5
Run func in a goroutine and wait for 1
Run func in a goroutine and wait for 3
Run func in a goroutine and wait for 1 end
Run Main function and wait for 2 done
Run func in a goroutine and wait for 2 end
Run func in a goroutine and wait for 3 end
Run func in a goroutine and wait for 4 end
Run func in a goroutine and wait for 5 end
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老孙正经胡说