Switch Fallthrough in Go

If you are familar with C or Java, you must know that break is requird for a switch's case branch, if break is missed, then it will fall through to next case.

For example, consider the following code

Java

int a = 1;

switch (a) {
    case 0: System.out.println("0");
    case 1: System.out.println("1");
    case 2: System.out.println("2"); break;
    default: System.out.println("unknown"); break;
}

The output is:

Bash

1
2

This is because, we don't have break in case 1, so it fall through to next branch case 2

Let's run the following golang code,

Go

var a = 1

switch a {
case 0:
fmt.Println("0")
case 1:
fmt.Println("1")
case 2:
fmt.Println("2")
default:
fmt.Println("unknown")
}

The output is 1.

This is because, the golang switch doesn't require a break, if it reach to the end of the code of the case branch, it ends the execution. But how can we archive the fall through like Java?

Golang, provides a keyword fallthrough, which supports to fall through to the next case branch.

Consider the following example,

Go

var a = 1

switch a {
case 0:
fmt.Println("0")
case 1:
fmt.Println("1")
fallthrough
case 2:
fmt.Println("2")
default:
fmt.Println("unknown")
}

The output is:

Bash

1
2

This is like what the above Java example.