What does this print? (Defer order during panic)

func main() {
	defer fmt.Println("1")
	defer func() {
		r := recover()
		fmt.Println("recovered", r)
	}()
	defer fmt.Println("3")
	fmt.Println(f())
	panic("boom")
}

func f() (n int) {
	defer func() { n *= 2 }()
	return 21
}

Output:

42
3
recovered boom
1

f: return 21 assigns n = 21, then deferred functions run and can change named results, so the caller gets 42. In main, a panic runs the deferred calls in LIFO order. "3" prints first. The next defer recovers "boom", which stops the panic, so the remaining defer ("1") still runs and main returns normally with exit code 0. Also note that arguments to a deferred call are evaluated when defer executes, not when the call runs. defer fmt.Println(x) captures the value of x at that moment.