func doSomething() {
    var i int
    for {
        i++
    }
}

func main() {

    cpu := runtime.NumCPU()
    fmt.Println("本机cpu核数:", cpu)

    fmt.Println("输入模拟的cpu数：")
    reader := bufio.NewReader(os.Stdin)
    buf, _ := reader.ReadBytes('\n')
    cmdStr := (string)(buf)
    num, err := strconv.Atoi(strings.Trim(cmdStr, "\r\n"))

    if err != nil || num > cpu || num <= 0 {
        fmt.Println("输入的数字不正确 err:{0}", err)
        return
    }

    //设置核数
    runtime.GOMAXPROCS(num)

    for i := 0; i < 10; i++ {
        //做个死循环
        go doSomething()
    }

    fmt.Println("程序已经开始执行")

    time.Sleep(time.Second * 30)

    for j := 5; j > 0; j-- {
        fmt.Printf("程序倒计时退出: %ds...\n", j)
        time.Sleep(time.Second)
    }
    fmt.Printf("程序退出")
}