Function spawn_thread 

pub fn spawn_thread<F, T>(f: F) -> JoinHandle<T>
where
    F: FnOnce() -> T + Send + 'static,
    T: Send + 'static,

Spawn a thread with test context propagation. If the spawned thread panics and the test uses DetachedPanicPolicy::FailTest (default), the panic will be reported as a test failure after the test body completes.