How to use flags with subcommands.

main.go

package main

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

func main() {
	verbose := flag.Bool("v", false, "verbose mode")
	prnt := flag.NewFlagSet("print", flag.ExitOnError)
	prntstrng := prnt.String("s", "", "string to print")
	prnt.Usage = func() {
		fmt.Fprintf(os.Stderr, "Usage of %s:\n", os.Args[0])
		flag.PrintDefaults()
		fmt.Fprintf(os.Stderr, "Usage of prnt:\n")
		prnt.PrintDefaults()
	}

	flag.Parse()

	switch flag.Args()[0] {
	case "help":
		fmt.Println("Usage of", os.Args[0])
		fmt.Println("\thelp\t\tThis command")
	case "prnt":
		prnt.Parse(flag.Args()[1:])
	}

	fmt.Println(*verbose, *prntstrng)

}