anchor.diff:  
   To https://vertx.io/docs/vertx-core/java/#golden_rule[avoid blocking the event loop], all you have to do is implement https://www.graphql-java.com/documentation/${graphql.java.doc.version}/data-fetching/[data fetchers] that return a `CompletionStage` instead of the result directly.
   
  -[source,java]
  +[source,$lang]
   ----
   {@link examples.GraphQLExamples#completionStageDataFetcher}
   ----
  
positive.code: 
  Eventually, configure the {@link io.vertx.ext.web.handler.graphql.GraphQLHandler} to create a `DataLoaderRegistry` for each request:
  
  [source,java]
  ----
  {@link examples.GraphQLExamples#dataLoaderRegistry}
  ----
  
negative.code: 
  This is where the {@link io.vertx.ext.web.handler.graphql.VertxDataFetcher} can help:
  
  [source,$lang]
  ----
  {@link examples.GraphQLExamples#vertxDataFetcher}
  ----
  