// same default value. They must be set up with an init function.
var gopherType string

func init() {
	const (
		defaultGopher = "pocket"
		usage         = "the variety of gopher"
	)
	flag.StringVar(&gopherType, "gopher_type", defaultGopher, usage)
	flag.StringVar(&gopherType, "g", defaultGopher, usage+" (shorthand)")
}

// Example 3: A user-defined flag type, a slice of durations.