flags.go

package main

import (
	"flag"
	"fmt"
	"os"
)

func cmd1(args []string) {
	fs := flag.NewFlagSet("cmd1", flag.ExitOnError)
	foo := fs.String("foo", "defaultfoo", "description of foo")
	fs.Parse(args)
	fmt.Println("value of foo", *foo)
}

func cmd2(args []string) {
	fs := flag.NewFlagSet("cmd2", flag.ExitOnError)
	bar := fs.String("bar", "defaultbar", "description of bar")
	fs.Parse(args)
	fmt.Println("value of bar", *bar)
}

func main() {
	if len(os.Args) < 2 {
		fmt.Println(`this is a help string

subcommands
	cmd1
	cmd2
`)
		os.Exit(2)
	}
	switch os.Args[1] {
	case "cmd1":
		cmd1(os.Args[2:])
	case "cmd2":
		cmd2(os.Args[2:])
	default:
		fmt.Println("unknown sub command:", os.Args[1])
	}
}