sync.WaitGroup

package main

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

	defer wg.Done()
	for j := range jobs {
	fmt.Println("我是 worker", id, "我要开始工作辣，我要处理", j)
		time.Sleep(time.Second) // 假装在工作
		results <- "我是 " + strconv.Itoa(id) + "，我处理完了" + strconv.Itoa(j)
	}
}

func main() {
	const numWorkers = 3
	const numJobs = 10

	jobs := make(chan int, numJobs)
	results := make(chan string, numJobs)

	var wg sync.WaitGroup

	// 启动 worker
	for w := 1; w <= numWorkers; w++ {
		wg.Add(1)
		go worker(w, jobs, results, &wg)
	}

	// 派发任务
	go func() {
		for j := 1; j <= numJobs; j++ {
			jobs <- j
		}
		close(jobs)
	}()

	// 等待所有 worker 完成，然后关闭 results
	go func() {
		wg.Wait()
		close(results)
	}()

	// 消费结果
	for r := range results {
		fmt.Println("result:", r)
	}
}

最佳实践：

• main 或启动 goroutine 的地方控制
• worker 只负责“干活”，不需要关心全局计数器