Hello.
I would like to thank you for helping me solve the problem.
I investigated a little and found that the dependency that is missing is from the "org.reactivestreams" and (in pom.xml) the maven code to insert and resolve the dependency would be this:
<dependency>
<groupId>org.reactivestreams</groupId>
<artifactId>reactive-streams</artifactId>
<version>1.0.1</version>
</dependency>
Hope this helps