Go Fallthrough: Purpose and Usage Explained

In Go language, the “fallthrough” keyword is used to continue executing the code block of the next case after one case is executed, without needing to check if the condition of the next case is met. Typically, when using a switch statement, if a case meets the condition, the code block of that case will automatically exit the switch statement and will not continue to execute the subsequent cases. However, using the “fallthrough” keyword can override this default behavior, allowing for the code block of the next case to be executed after the condition of the current case is met.

Here is an example of using the “fallthrough” keyword:

package main

import "fmt"

func main() {
    num := 2
    switch num {
    case 1:
        fmt.Println("Num is 1")
        fallthrough
    case 2:
        fmt.Println("Num is 2")
        fallthrough
    case 3:
        fmt.Println("Num is 3")
    }
}

In the example above, when the value of num is 2, after executing the code block of case 2, the fallthrough keyword is used, which will continue to execute the code block of the next case. The output result is:

Num is 2
Num is 3

It is important to note that the “fallthrough” keyword can only be used in a switch statement and must only appear at the end of a code block within a case.