public final CompletableFuture<Void> stop() {
        return stop(null);
    }
Begins the shutdown procedure without an argument by calling {@link #doStop(Object)}, ensuring that
neither {@link #doStart(Object)} nor {@link #doStop(Object)} is invoked concurrently. This method is
a shortcut of {@code stop(null)}.
core/src/main/java/com/linecorp/armeria/common/util/StartStopSupport.java