switch Statement

A switch statement selects a branch based on a value or a set of conditions. It often reads more clearly than a long chain of checks for the same expression.

In an expression switch, Go compares the switch expression with each case value. Once a matching case runs, it exits the switch automatically; most switches need no break. A default clause handles unmatched values.

You can list several matching values in one case, separated by commas. A switch without an expression is also valid and checks boolean conditions in order.

Follow this diagram before executing the example. Check where a value or decision changes what runs next.

This example is a complete program. Save it as main.go or paste it into the Go Playground.

Go code

package main

import "fmt"

func main() {
	day := "Sunday"
	switch day {
	case "Saturday", "Sunday":
		fmt.Println("Weekend")
	case "Monday":
		fmt.Println("Start of the week")
	default:
		fmt.Println("Weekday")
	}
}

Output

Weekend

The value Sunday matches the first case, which lists two possible strings. Go prints Weekend and exits the switch without executing any other cases. It does not fall through by default.

• Unlike C-style switches, Go cases do not automatically fall through.
• Cases can be grouped with commas; case "Saturday" || "Sunday" is not valid for switching on a string.

Change the day to Tuesday and predict which clause runs. Add a case for Friday with a new message.

Tip: Edit the example above, predict the output, and run the modified code to test your reasoning.

You have practiced Go switch Statement in a small, self-contained program. The important habit is to predict what runs, inspect the actual output and distinguish the language rule from the particular example.

Before continuing, make sure you can explain the program to someone who has not seen it, including the line that changes its result.