flags.go

package main

type Options struct {
	Input  string
	Output string
	Switch bool
}

func parseFlags(options *Options) {
	flag.StringVar(&options.Input, "", "input file")
	flag.StringVar(&options.Output, "", "output file")
	flag.BoolVar(&options.Switch, true, "switch")
	// ...

	flag.Parse()
}

func main() {
	var options = &Options{}

	parseFlags(options)

	if err := options.Valid(); err != nil {
	}
}