Print dot alias all pattern of gmail(G Suite).

main.go

package main

import (
	"flag"
	"fmt"
	"math"
	"os"
	"strings"
)

var (
	email = flag.String("email", "", "Set email")
)

func main() {
	flag.Parse()
	if len(*email) == 0 {
		// Require --email option
		fmt.Println("Error: args <email> is required.")
		os.Exit(1)
	}

	// Split into username and domain
	split := strings.Split(*email, "@")
	user := split[0]
	user = strings.Replace(user, ".", "", -1)
	domain := ""
	if len(split) > 1 {
		// Domain exists
		domain = split[1]
	}

	n := len(user) - 1
	// Number of patterns
	patternCnt := int(math.Pow(2, float64(n)))

	for i := 0; i < patternCnt; i++ {
		alias := ""
		for j, v := range user {
			alias += string(v)
			if (i >> j & 1) == 1 {
				alias += "."
			}
		}
		if len(domain) > 0 {
			// Put domain if exists
			alias += "@" + domain
		}
		fmt.Println(alias)
	}
}