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Terminating statements

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8. A labeled statement labeling a terminating statement.

Labeled statement’s are not used a lot in Go. Terminating labeled statements even less so. But they do exist, just the same. Here’s an example, using goto, and a labeled terminating statement.

func foo() {
	if someCondition {
		goto end
	}
	fmt.Println("unf")
end:
	return
}

Here end is a label, that labels the statement return. Since the label labels a terminating statement, the labeled statement terminates. Funny how that works.

Can we have a labeled terminating statement that isn’t the target of goto?

Well, labels can be the target of goto, break, or continue. We already saw an example of goto. So what about the others?

A break can only ever be referred to from within for loops or select or switch statements, and adding a break to any of these renders the block that contains it no longer terminating.

So that leaves continue. continue can reference a terminating statement, if the loop it’s in is terminating:

loop:
	for {
		continue loop
	}

Silly example of an infinite loop, but it is terminating.

Here’s a plausibly more realistic example:

  var i int

loop:
	for {
		i++
		if i > 10 {
			return
		}
		continue loop
	}

Obviously using continue in both of these examples is silly, as that would be the default behavior anyway. But I trust you can imagine that there’s some other logic to make the use of continue meaningful.

Quotes from The Go Programming Language Specification Language version go1.22 (Feb 6, 2024)