Function spawn_local 

pub fn spawn_local<F>(future: F) -> Task<F::Output> 
where
    F: Future + 'static,
    F::Output: 'static,

Spawns a task that stays on the calling thread: a worker’s shard, or the thread’s own (where it runs while the thread is inside block_on). The future need not be Send.

Panics

When this thread’s shard cannot start (its poller cannot be made); task::Builder::spawn_local answers the error instead.