|  | 
           
Stop the io_context object's event processing
          loop.
        
void stop();
          This function does not block, but instead simply signals the io_context to stop. All invocations
          of its run()
          or run_one()
          member functions should return as soon as possible. Subsequent calls to
          run(),
          run_one(),
          poll()
          or poll_one()
          will return immediately until restart() is called.