reactor-core/src/main/java/reactor/core/publisher/Mono.java
public Optional<T> blockOptional(Duration timeout) {
		BlockingOptionalMonoSubscriber<T> subscriber = new BlockingOptionalMonoSubscriber<>();
		Operators.onLastAssembly(this).subscribe(Operators.toCoreSubscriber(subscriber));
		return subscriber.blockingGet(timeout.toMillis(), TimeUnit.MILLISECONDS);
	}
public Optional<T> blockOptional(Duration timeout) {
		BlockingOptionalMonoSubscriber<T> subscriber = new BlockingOptionalMonoSubscriber<>();
		Operators.onLastAssembly(this).subscribe(Operators.toCoreSubscriber(subscriber));
		return subscriber.blockingGet(timeout.toMillis(), TimeUnit.MILLISECONDS);
	}
Subscribe to this {@link Mono} and <strong>block</strong> until a next signal is
received, the Mono completes empty or a timeout expires. Returns an {@link Optional}
for the first two cases, which can be used to replace the empty case with an
Exception via {@link Optional#orElseThrow(Supplier)}.
In case the Mono itself errors, the original exception is thrown (wrapped in a
{@link RuntimeException} if it was a checked exception).
If the provided timeout expires, a {@link RuntimeException} is thrown.

<p>
<img class="marble" src="doc-files/marbles/blockOptionalWithTimeout.svg" alt="">
<p>
Note that each block() will trigger a new subscription: in other words, the result
might miss signal from hot publishers.

@param timeout maximum time period to wait for before raising a {@link RuntimeException}

@return T the result