main.go

package main

import (
	"flag"
	"fmt"
	"os/exec"
	"sync"
)

var (
	parallel = flag.Bool("parallel", true, "")
)

func download(url string) error {
	fmt.Printf("Start to download: %s\n", url)
	cmd := exec.Command("wget", url)
	return cmd.Run()
}

func main() {
	flag.Parse()

	args := flag.Args()

	if *parallel {
		wg := new(sync.WaitGroup)
		for _, v := range args {
			wg.Add(1)
			go func() {
				defer wg.Done()
				download(v)
			}()
		}
		wg.Wait()
	} else {
		for _, v := range args {
			download(v)
		}
	}
}