void cancelSchedule() {
            if (timeoutFuture != null && !timeoutFuture.isCancelled()) {
                timeoutFuture.cancel(false);
            }
        }
Subscribes the given subscriber to this stream with timeout logic applied.

@param subscriber the subscriber to this stream
@param executor the executor for running timeout tasks and stream operations
@param options subscription options
@see StreamMessage#subscribe(Subscriber, EventExecutor, SubscriptionOption...)
core/src/main/java/com/linecorp/armeria/common/stream/TimeoutStreamMessage.java