Last week we saw that a block that ends in a terminaging statement is itself a terminating statement.

Today we expand a bit on that idea:

Terminating statements

…

4. An “if” statement in which:

   • the “else” branch is present, and
   • both branches are terminating statements.

In other words, the following counts as a terminating statement:

if somethingInterestingHappened() {
	fmt.Println("Wow, that was interesting!")
	return
} else {
	fmt.Println("That was boring.")
	return
}

Both branches of the if statement terminate, so the statement as a whole is a terminating statement. Put another way: There’s no possible way any code following this block would be executed, therefore it is terminating.

What would make this not-terminating?

1. Obviously, if we remove either return statement
2. If the else were replaced with an else if
3. If we add some statement to either block that breaks out of otherwise normal flow control (such as a goto, continue, or break—assuming, of course, this code is part of a relevant loop or select statement.)

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