main函数中如何等待协程运行完毕

使用channel同步

package main
import (
    "fmt"
)

func printNumber(num int, c chan struct{}) {
  fmt.Println(num)
  c <- struct{}{}
}

func main() {
  sign := make(chan struct{}, 10)
  for i:=0;i<10;i++ {
    go printNumber(i, sign)
  }
  for i:=0;i<10;i++{
    <-sign
  }
  fmt.Println("Done.")
}

使用sync.WaitGroup

package main
import (
    "fmt"
    "sync"
)

func printNumber(num int, callback func()) {
  fmt.Println(num)
  callback()
}

func main() {
  var wg sync.WaitGroup
  wg.Add(10)
  for i:=0;i<10;i++ {
    go printNumber(i, wg.Done)
  }
  wg.Wait()
  fmt.Println("Done.")
}