waitgroup等待退出

package main

import (
   "fmt"
   "sync"
   "time"
)

func main() {
   wg := sync.WaitGroup{}
   for i := 0; i < 10; i++ {
      wg.Add(1)
      go calc(&wg, i)
   }
   wg.Wait()
   fmt.Println("all goroutine finish")
}

func calc(w *sync.WaitGroup, i int) {
   fmt.Println("calc", i)
   time.Sleep(time.Second)
   w.Done()
}