How to lookup a flag from os.Args in Go

lookupFlag.go

package main

import (
	"fmt"
	"os"
	"strings"
)

func LookupFlag(name string) (value string, found bool) {
	i := 0
	for i < len(os.Args) {
		flg := os.Args[i]
		if len(flg) == 0 || flg[0] != '-'{
			i++
			continue
		}
		// we have a flag
		foundName, val := parseFlag(flg, i)
		if foundName == name {
			return val, true
		}
		i++
	}
	return "", false
}

func parseFlag(flag string, atIndex int) (name string, val string) {
	flag = strings.TrimPrefix(flag, "-")
	flag = strings.TrimPrefix(flag, "-")
	if strings.Contains(flag, "=") {
		split := strings.Split(flag, "=")
		// This should be safe because of our contains check
		return split[0], split[1]
	}
	// else check the next os arg
	if len(os.Args) > atIndex+1 {
		nextFlag := os.Args[atIndex+1]
		if !strings.HasPrefix(nextFlag, "-") {
			return flag, nextFlag
		}
	}
	// boolean flag
	return flag, "true"
}

func main() {
	os.Args = []string{"--dogs=2","-cats","false","-horses","--ducks","many"}
	val, ok := LookupFlag("dogs")
	fmt.Println(val, ok)
	val, ok = LookupFlag("cats")
	fmt.Println(val, ok)
	val, ok = LookupFlag("horses")
	fmt.Println(val, ok)
	val, ok = LookupFlag("cows")
	fmt.Println(val, ok)
	val, ok = LookupFlag("ducks")
	fmt.Println(val, ok)
}