A custom command line flag `-junk`

junk.go

package junk

import (
	"flag"
	"fmt"
	"strconv"
)

type Junk int64

type junkFlag struct{ Junk }

func (j Junk) String() string {
	return fmt.Sprintf("JUNK->%d<-JUNK", j)
}

func (j *junkFlag) Set(s string) error {
	i, err := strconv.ParseInt(s, 10, 32)
	if err != nil {
		return err
	}
	j.Junk = Junk(i)
	return nil
}

func JunkFlag(name string, amount Junk, usage string) *Junk {
	j := junkFlag{amount}
	flag.CommandLine.Var(&j, name, usage)
	return &j.Junk
}