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Go join string

last modified January 9, 2023

Go join string tutorial shows how to join strings in Golang.

To join strings, we can use the + operator, fmt.Sprintf function, and strings.Join function. 

$ go version
go version go1.18.1 linux/amd64

We use Go version 1.18.

Go join strings with + operator

Many programming languages use the + operator to join strings.

main.go
package main

import "fmt"

func main() {

    w1 := "old"
    w2 := "falcon"

    msg := w1 + " " + w2

    fmt.Println(msg)
}

Two words are joined in the example. We also add a space character between them. 

$ go run main.go 
old falcon

Go join strings with fmt.Sprintf

The fmt.Sprintf function builds a string according to the given format specifiers and returns the resulting string.

main.go
package main

import "fmt"

func main() {

    w1 := "old"
    w2 := "falcon"

    msg := fmt.Sprintf("%s %s", w1, w2)

    fmt.Println(msg)
}

The example builds a message by joining two words.

Go join strings with bytes.Buffer

A bytes.Buffer is a variable-sized buffer of bytes with Read and Write methods.

main.go
package main

import (
    "bytes"
    "fmt"
)

func main() {

    var buf bytes.Buffer

    buf.WriteString("an ")
    buf.WriteString("old ")
    buf.WriteString("falcon")

    fmt.Println(buf.String())
}

In the example, we write strings to the bytes buffer with WriteString and then convert the bytes into a final string with String function. 

$ go run main.go 
an old falcon

Go strings.Join

The strings.Join function joins string elements of a slice/array into one string. The separator string is placed between elements in the resulting string.

fmt_funs.go
package main

import (
    "fmt"
    "strings"
)

func main() {

    words := []string{"an", "old", "falcon"}
    msg := strings.Join(words, " ")

    fmt.Println(msg)
}

We have a slice of words. We join them with strings.Join, utilizing a single space as a separator.

Go String function

The String function of an object is called when it is passed to any of the print functions. It is commonly used to display a human-readable representation of the object.

main.go
package main

import (
    "fmt"
)

type User struct {
    Name       string
    Occupation string
}

func (u User) String() string {

    return fmt.Sprintf("%s is a(n) %s", u.Name, u.Occupation)
}

func main() {

    u1 := User{"John Doe", "gardener"}
    u2 := User{"Roger Roe", "driver"}

    fmt.Println(u1)
    fmt.Println(u2)
}

In the example, we use the fmt.Sprintf function to generate an output of a User type. 

$ go run main.go 
John Doe is a(n) gardener
Roger Roe is a(n) driver

In this article, we have showed how to join strings in Golang.

List all Go tutorials.