why multithreading execition take time almost equal to single thread execution?

[SergeyPython]

Thx for your example. It's like middle level of handling futures. Is where any 
high level Nim API for handle futures? Like this in Python:
    
    
    ...
            with ThreadPoolExecutor(thread_name_prefix='Transport', 
max_workers=20) as executor:
                executor.submit(self.delman.handle_message, tag=tag) \
                    .add_done_callback(self.handle_future)
    
    
    Run