Stop an asynchronous Aio operation.
stop_aio(aio)an Aio (object of class 'sendAio', 'recvAio' or 'ncurlAio').
Invisible NULL.
Stops the asynchronous I/O operation associated with 'aio' by aborting, and then waits for it to complete or to be completely aborted, and for the callback associated with the 'aio' to have completed executing. If successful, the 'aio' will resolve to an 'errorValue' 20 (Operation canceled).
Note this function operates silently and does not error even if 'aio' is not an active Aio, always returning invisible NULL.