custom_usage.go

package main

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

func usage() {
	banner := `toqoz is useless tool

Usage:

    toqoz [sub-command]

The sub-commands are:

    create
    destroy

The options are:

`
	fmt.Fprintf(os.Stderr, banner)
	flag.PrintDefaults()
	fmt.Fprintf(os.Stderr, "\n")
	os.Exit(1)
}

func main() {
	flag.Usage = usage
	flag.Parse()

	switch flag.Arg(0) {
	case "create":
		// do something
	case "destroy":
		// do something
	default:
		flag.Usage()
	}
}