Go String

What is a string?

A string is a sequence of characters (letters, numbers, symbols, emojis, etc.). Here are some examples of strings:

"Hello, World!", "Hello, 世界", "Hello, 🌍", etc.

They are enclosed in double quotes (") and have the type string.

How to declare a string and access its characters?

There are two ways to declare a string in Go.

• Using double quotes
• Using backticks

Declaring a string in Go using double quotes

Like for all other types, you can declare a string variable using the var keyword:

var s string = "Hello, World!"

Or you can use the short variable declaration operator :=:

s := "Hello, World!"

Accessing characters of a string in Go

To access a character in a string, you can use the square brackets ([]) operator:

package main

import "fmt"

func main() {
    s := "Hello, World!"

    // Print the Unicode Code points
    fmt.Println(s[0]) // 72
    fmt.Println(s[7]) // 87
}

Output

72
87

Note: 72 and 87 are the Unicode code points of the characters H and W, respectively. To print the characters themselves, you can use fmt.Printf:

package main

import "fmt"

func main() {
    s := "Hello, World!"
    fmt.Printf("%c", s[0]) // H
    fmt.Printf("%c", s[7]) // W
}

Output

H
W

Note: The characters are accessed using their index number, and the index starts from 0, not from 1.

But you can't use the square brackets operator to update a character in a string:

s := "Hello, World!"
s[0] = 'h' // error: cannot assign to s[0]

This is because strings are immutable in Go. So once it's created, we cannot modify the contents of the string.

Declare and access strings using backtick

In Go, String literals are created using backticks (``). Hence, it is also called raw literals.

The string literals do not support escape characters, but they can span over multiple lines. Therefore, it is mainly used to declare longer strings spanning multiple lines.

package main

import "fmt"

func main() {
    s := `Hello, World!
    Welcome to Go Programming`
    fmt.Println(s)
}

Output

Hello, World!
    Welcome to Go Programming

Find the length of a string

We can find the length of a string using the len() method. The len() function returns the total count of characters in a given string.

package main

import "fmt"

func main() {
    s := "Hello, World!"
    fmt.Println("The length of the string is:", len(s))
}

Output

The length of the string is: 13

Useful string methods

Go provides several useful methods for strings:

• Compare to compare two strings
• ToUpper and ToLower to convert a string to upper or lower case,
• Contains to check if a string contains a substring,
• Replace to replace a substring with another substring,
• Split to split a string into a slice of strings based on a separator,
• Trim to remove leading and trailing characters from a string (for example, when dealing with files and user input).

Here is how to use them:

package main

import (
    "fmt"
    "strings"
)

func main() {
    s := "Hello, World!"
    t := "Hello, World!"
    fmt.Println(strings.Compare(s, t))                      // 0
    fmt.Println(strings.ToUpper(s))                         // HELLO, WORLD!
    fmt.Println(strings.ToLower(s))                         // hello, world!
    fmt.Println(strings.Contains(s, "Hello"))               // true
    fmt.Println(strings.Replace(s, "World", "世界", 1))       // Hello, 世界!
    fmt.Println(strings.Split(s, " "))                      // [Hello World!]
    fmt.Println(strings.Trim("    Hello, World!    ", " ")) // Hello, World!
}

Output

0
HELLO, WORLD!
hello, world!
true
Hello, 世界!
[Hello, World!]
Hello, World!

The strings package of the standard library contains many more useful methods for strings that you can find in the documentation.