useinstant::Instant;/// Clock returns the current time.
pubtraitClock{fnnow(&self)-> Instant;}/// `SystemClock` uses the system's clock to get the current time.
/// This Clock should be used for real use-cases.
#[derive(Debug, Default)]pubstructSystemClock{}implClock forSystemClock{fnnow(&self)-> Instant{Instant::now()}}