custom typed args

args_example_custom_type.go

var port = args.NewInt(args.Flag("example.typed.port", 1234, "the port"))
var roundTripper = args.New(args.Default(http.DefaultTransport))
var timeout = args.NewDuration()

type ServerOpt args.V

func Port(p int) ServerOpt                 	  { return ServerOpt(port(p)) }
func RoundTripper(r http.RoundTrippper) ServerOpt { return ServerOpt(roundTripper(r)) }
func Timeout(d time.Duration) ServerOpt           { return ServerOpt(timeout(d)) }

func MyServer(opts ...ServerOpt) {
	port := port.Get(opts)
	fmt.Printf("listening on port %v\n", port)

	rt := roundTripper.Get(opts).(http.RoundTripper)
	if rt == http.DefaultTransport {
		fmt.Println("using the default transport")
	} else {
		fmt.Println("using a user-provided round-tripper")
	}

	to := timeout.Get(opts)
	fmt.Printf("using a timeout of %v\n", to)
}