Do Go switch/cases fallthrough or not?

go switch-statement fall-through
mcandre picture mcandre · Nov 26, 2016 · Viewed 40.1k times · Source

What happens when you reach the end of a Go case, does it fall through to the next, or assume that most applications don't want to fall through?

Answer

Sam Whited picture Sam Whited · Nov 26, 2016

No, Go switch statements do not fall through by default. If you do want it to fall through, you must explicitly use a fallthrough statement. From the spec:

In a case or default clause, the last non-empty statement may be a (possibly labeled) "fallthrough" statement to indicate that control should flow from the end of this clause to the first statement of the next clause. Otherwise control flows to the end of the "switch" statement. A "fallthrough" statement may appear as the last statement of all but the last clause of an expression switch.

For example (sorry, I could not for the life of me think of a real example):

switch 1 {
case 1:
    fmt.Println("I will print")
    fallthrough
case 0:
    fmt.Println("I will also print")
}

Outputs:

I will print
I will also print

https://play.golang.org/p/va6R8Oj02z

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