Example of a more complex kingpin setup.

main.go

package main

import (
	"fmt"
	"os"

	"github.com/alecthomas/kingpin"
)

var (
	app = kingpin.New("chat", "A command-line chat application.")

	verbose = app.Flag("verbose", "Verbose mode.").Short('v').Bool()

	username = app.Flag("username", "Username used to authenticate to service.").Required().String()
	password = app.Flag("password", "Password used to authenticate to service.").Required().String()

	register = app.Command("register", "Register a new user.")

	post = app.Command("post", "Post a message to a channel.")
)

type RegisterFlags struct {
	RegisterNick string
}

type PostFlags struct {
	PostNick string
}

func registerSetup() *RegisterFlags {
	rf := &RegisterFlags{}

	register.Flag("nick", "The nick name you want to register.").Short('n').StringVar(&rf.RegisterNick)

	return rf
}

func postSetup() *PostFlags {
	rf := &PostFlags{}

	post.Flag("nick", "The nick name you want to register.").Short('n').StringVar(&rf.PostNick)

	return rf
}

func main() {

	rf := registerSetup()
	pf := postSetup()

	switch kingpin.MustParse(app.Parse(os.Args[1:])) {
	// Register user
	case register.FullCommand():

		fmt.Println("Register", rf)
	// Post message
	case post.FullCommand():
		fmt.Println("Post", pf)
	}

}

$ go run cmd/kingpinlol/main.go --help-long
usage: chat --username=USERNAME --password=PASSWORD [<flags>] <command> [<args> ...]

A command-line chat application.

Flags:
      --help               Show context-sensitive help (also try --help-long and --help-man).
  -v, --verbose            Verbose mode.
      --username=USERNAME  Username used to authenticate to service.
      --password=PASSWORD  Password used to authenticate to service.

Commands:
  help [<command>...]
    Show help.


  register [<flags>]
    Register a new user.

    -n, --nick=NICK  The nick name you want to register.

  post [<flags>]
    Post a message to a channel.

    -n, --nick=NICK  The nick name you want to register.