1.非併發

package main

import (
    "fmt"
    "net"
)

func main() {
    for i := 21; i < 120; i++ {
        address := fmt.Sprintf("192.168.90.1:%d", i)
        conn, err := net.Dial("tcp", address)
        if err != nil {
            fmt.Printf("%s 關閉了 \n", address)
            continue
        }
        conn.Close()
        fmt.Printf(
 
"%s 打開了！！！\n", address)
    }
}

結果：

2.併發

package main

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

func main() {
    start := time.Now()
    var wg sync.WaitGroup //計數器
    for i := 21; i < 120; i++ {
        wg.Add(1) //加一
        //每次迴圈建立一個 go func
        go func(j int) {
            defer wg.Done() 
 
//減1
            address := fmt.Sprintf("192.168.90.1:%d", j)
            conn, err := net.Dial("tcp", address)
            if err != nil {
                fmt.Printf("%s 關閉了 \n", address)
                return
            }
            conn.Close()
            fmt.Printf("%s 打開了！！！\n", address)
        }(i)
    }
    wg.Wait()                         
 
//直到wg計數器位0放行
    elapse := time.Since(start) / 1e9 //執行時長
    fmt.Printf("\n %d second:", elapse)
}

結果：

感謝：https://www.bilibili.com/video/BV13K4y1a7dt?p=3