• Dart

Future.delayed(const Duration(seconds: 30), () => f(42));

• Clojure

(do (Thread/sleep 30000)
    (f 42))

• C#

Task.Delay(TimeSpan.FromSeconds(30))
    .ContinueWith(_ => f(42));

• Go

timer := time.AfterFunc(
	30*time.Second,
	func() {
		f(42)
	})

• Go

go func() {
	time.Sleep(30 * time.Second)
	f(42)
}()

• Groovy

sleep(30*1000)
f(42)

• JS

let id = setTimeout(f, 30000, 42);

• Java

ScheduledExecutorService executorService = Executors.newSingleThreadScheduledExecutor();
executorService.schedule(() -> _f(42), delayInSeconds, TimeUnit.SECONDS);

• Java

Thread t = new Thread(() -> {
    try {
        sleep(30_000);
        f(42);
    } catch (InterruptedException e) {
        throw new RuntimeException(e);
    }
});
t.start();

• PHP

sleep(30);
f(42);

• Perl

my $thr = threads->create(sub { sleep(30); f(42); });
$thr->join()

• Perl

my $thr = threads->create(sub { sleep(30); f(42); });
$thr->detach();

• Perl

local $SIG{ALRM} = sub { f(42) };
alarm 30;

• Python

timer = threading.Timer(30.0, f, args=(42,) ) 
timer.start() 

• Ruby

Thread.new do
  sleep 30
  f(42)
end

• Rust

sleep(Duration::new(30, 0));
f(42);

• Smalltalk

(f future: 30 "seconds" * 1000) value: 42.