Go Basics

Go Strings and the strings Package

Join, search, split, trim and slice text in Go.

Beginner
2 min read
1 runnable example

What you'll learn

Building strings
Contains, Index, Split
Slicing a string

Run code →

message[0:5]

The end index 5 is not included.

Read-only text with many helpers

A Go string is a read-only sequence of bytes, usually UTF-8 text. You cannot change a string in place, but you can build new ones, and the strings package has functions for most everyday jobs.

+= builds a new string. len counts bytes. Contains and Index search the text, Split cuts it at a separator and returns a slice, and message[0:5] takes the bytes from position 0 up to, but not including, 5.

Key points

A string cannot be changed in place.
len counts bytes.
message[0:5] takes bytes 0 to 4.

Runnable Go example

Run code →

main.go

package main

import (
	"fmt"
	"strings"
)

func main() {
	message := "Hello, Go"
	message += "!"

	fmt.Println(message)
	fmt.Println(len(message), strings.ToUpper(message))
	fmt.Println(strings.Contains(message, "Go"), strings.Index(message, "Go"))
	fmt.Println(strings.Split("a,b,c", ","))
	fmt.Println(strings.Repeat("=", 5), strings.TrimSpace("  padded  "))
	fmt.Println(message[0:5], string(message[7]))
}

Get a Run button for this example Result of running the code

Hello, Go!
10 HELLO, GO!
true 7
[a b c]
===== padded
Hello G

Practice

Open the example in the online compiler, change a value or add a line, and predict the output before you run it. Then break the code on purpose and read the compiler's message.

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