What is the fallthrough keyword in Go?

Overview

In Go, switch statements are case-oriented, and a case block will execute if the specified condition is matched. The keyword fallthrough allows us to execute the next case block without checking its condition. In other words, we can merge two case blocks by using the keyword fallthrough.

Syntax

case x:
  // add content of case block here
  fallthrough
case y:    //the next case block

In Go, fallthrough is not the default behavior. We have to mention it explicitly.

Demo code

package main
import "fmt"
func main() {
  num := 0
  switch num { 
    case 0:
      fmt.Println("Case: 0")
      fallthrough   // Case 1 will also execute
    case 1:
      fmt.Println("Case: 1")
    case 2:
      fmt.Println("Case: 2")
    default:
      fmt.Println("default")
  }
}

Explanation

  • Line 9: The keyword fallthrough transfers the control to the first line of the case 1 block, so that this block also gets executed.

The keyword fallthrough must be the last non-empty line of a case block. Otherwise, it will not work.

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