Golang sync.WaitGroup用法举例2

package main

import (
    "fmt"
    "sync"
)

func main() {
    hello := func(wg *sync.WaitGroup, id int) {
        defer wg.Done()
        fmt.Printf("hello from %v\n", id)
    }

    numGreeters := 5
    var wg sync.WaitGroup
    wg.Add(numGreeters)

    for i := 0; i < numGreeters; i++ {
        go hello(&wg, i+1)
    }
    wg.Wait()
}