public ClientFactoryBuilder workerGroup(int numThreads) {
        return workerGroup(EventLoopGroups.newEventLoopGroup(numThreads), true);
    }
Uses a newly created {@link EventLoopGroup} with the specified number of threads for
performing socket I/O and running {@link Client#execute(ClientRequestContext, Request)}.
The worker {@link EventLoopGroup} will be shut down when the {@link ClientFactory} is closed.

@param numThreads the number of event loop threads
core/src/main/java/com/linecorp/armeria/client/ClientFactoryBuilder.java