Concatenate a string and an int in Go

Published: May 24, 2019

Tags:

• Go
• Golang

Improve this page on GitHub

Recently I needed to concatenate a string and an int in Go. Googling revealed an overwhelming number of options. I’ve gathered and organized all of them in this post, including full working examples for each.

NOTE: This example concatenate the integer 1 with the string "[email protected]" to form the string "[email protected]".

fmt.Sprintf

One option is to use fmt.Sprintf. Implementation looks like this:

package main

import (
	"fmt"
)

func main() {
	num := 1
	email := "[email protected]"
	concatenated := fmt.Sprintf("%d%s", num, email)

	fmt.Println(concatenated)
}

fmt.Sprint

I personally always forget the tokens to pass to fmt.Sprintf. fmt.Sprint makes things easier:

package main

import (
	"fmt"
)

func main() {
	num := 1
	email := "[email protected]"
	concatenated := fmt.Sprint(num, email)

	fmt.Println(concatenated)
}

strconv.Itoa

You can also use strconv.Itoa to convert an int to a string. You can then concatenate with +. Coming from a PHP and JavaScript background I personally find this to be the most readable / understandable.

package main

import (
	"fmt"
	"strconv"
)

func main() {
	num := 1
	email := "[email protected]"
	concatenated := strconv.Itoa(num) + email

	fmt.Println(concatenated)
}

I’ve also seen suggestions to use strings.Join instead of +. I find this to be the least readable of the all the options but apparently it performs slightly better.

package main

import (
	"fmt"
	"strconv"
	"strings"
)

func main() {
	num := 1
	email := "[email protected]"
	concatenated := strings.Join([]string{strconv.Itoa(num), email}, "")

	fmt.Println(concatenated)
}