go练习例子

1.wg

package main

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

var wg sync.WaitGroup

func printNumbers() {
    defer wg.Done()
    for i := 1; i <= 5; i++ {
        fmt.Println(i)
        time.Sleep(time.Second)
    }
}

func main() {
    wg.Add(1)
    go printNumbers()
    wg.Wait()
}