與Channel區別
Channel能夠很好的幫助我們控制并發，但是在開發習慣上與顯示的表達不太相同，所以在Go語言中可以利用sync包中的WaitGroup實現并發控制，更加直觀。
基本使用示例
我們將之前的示例加以改造，引入sync.WaitGroup來實現并發控制。
? 首先我們在主函數中定義WaitGroup
? 每執行一個任務，則調用Add()方法
? 在主函數中我們利用Wait()方法等待并發結束
? 在調用的函數中，我們需要將WaitGroup以指針方式傳入，否則將造成Deadlock
// 主函數內
go ready(5, &wg)
// 函數
func ready(s int, wg *sync.WaitGroup)
? 同時在函數執行完成后，調用wg.Done，我們使用defer實現
完整代碼
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()
}
特別提示
WaitGroup傳入給函數時，需要以指針方式傳遞，否則會造成Deadlock
多任務示例
如果不想在函數中傳遞WaitGroup，也可以采用以下這種方式，通過并發匿名函數的方式，在主函數邏輯中對并發進行精準控制
var wg sync.WaitGroup
for i := 0; i < 5; i++ {
wg.Add(1)
waitSec := i + 1
go func() {
defer wg.Done()
ready(waitSec)
}()
}
完整代碼
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()
}
運行結果如下
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
