Function spawn 

pub fn spawn<F>(future: F) -> JoinHandle<F::Output> 
where
    F: Future + Send + 'static,
    F::Output: Send + 'static,

Spawns a future onto the current thread’s runtime

This is a convenience function that uses a thread-local runtime. For DLL boundary safety, create and use an explicit Runtime instead.

This function is only available when the std feature is enabled.