Golang 协程 TCP 扫描提前退出：如何确保所有协程完成任务？

package main

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

func scanPort(jobChan <-chan int, retChan chan<- string, wg *sync.WaitGroup) {
    defer wg.Done()

    for port := range jobChan {
        target := fmt.Sprintf("149.129.68.235:%d", port)
        _, err := net.DialTimeout("tcp", target, 100*time.Millisecond)
        if err == nil {
            retChan <- fmt.Sprintf("%s is open", target)
        }
    }
}

func main() {
    jobChan := make(chan int, 5)
    retChan := make(chan string, 5)

    go func() {
        for i := 0; i < 1024; i++ {
            jobChan <- i
        }
        close(jobChan)
    }()

    wg := sync.WaitGroup{}

    // 创建n个协程
    for i := 0; i < 10; i++ {
        wg.Add(1)
        go scanPort(jobChan, retChan, &wg)
    }

    // 输出结果
    go func() {
        for ret := range retChan {
            fmt.Println(ret)
        }
    }()

    // 等待协程完成
    wg.Wait()
    close(retChan)
}