multiflag.go

package main

import (
	"flag"
	"fmt"
)

type strslice []string

func (s *strslice) String() string {
	return fmt.Sprintf("%v", *s)
}

func (s *strslice) Set(v string) error {
	*s = append(*s, v)
	return nil
}

func main() {
	var multiflag strslice

	flag.Var(&multiflag, "data", "Data values.")
	flag.Parse()

	fmt.Printf("%v", multiflag)
}