Golang program with single argument.go

package main

import (
	"fmt"
	"os"
	"flag"
	"path/filepath"
)

func usage() {
	fmt.Fprintf(os.Stderr, "usage: %v arg\n", filepath.Base(os.Args[0]))
	os.Exit(2)
}

func main() {
	flag.Usage = usage
	flag.Parse()
	if flag.NArg() == 0 {
		usage()
	}

	arg := flag.Arg(0)
}