An example for providing multiple values to the same command line parameter - with builtin `flag` in Go

mutliflag.go

// Package main shows an example for providing multiple values to the same
// command line parameter - with builtin `flag` in Go.
package main

import (
	"flag"
	"fmt"
	"strings"
)

// Create a type
type multiValue []string

// On which the interface Stringer is implemented
func (values *multiValue) String() string {
	return strings.Join([]string(*values), "\n")
}

// Also the method Set must be implemented
func (values *multiValue) Set(value string) error {
	*values = append(*values, value)
	return nil
}

// Then the usage is like this.
// Use `flag.Var` as the type, then each value will be in the slice.
func main() {
	var multiFlag multiValue
	flag.Var(&multiFlag, "value", "provide one by one: `--value value1 --value \"value with whitespace in\"`")
	flag.Parse()
	fmt.Println(&multiFlag)
}