Function spawn 

pub fn spawn<T, F>(name: &str, future: F) -> JoinHandle<T> 
where
    F: Future<Output = T> + Send + 'static,
    T: Send + 'static,

Spawn a named task onto the executor currently running on this thread.

The returned JoinHandle mirrors tokio semantics: awaiting it yields the task’s output (or a JoinError if the task was aborted or panicked), dropping it detaches the task, and JoinHandle::abort cancels it.

Panics

Panics when called outside Executor::block_on, mirroring tokio::spawn outside a runtime.