code: protected <V> CompletableFuture<V> callAsync(Callable<V> callable, Time timeout) {
  		return rpcServer.callAsync(callable, timeout);
  	}
docs: Execute the callable in the main thread of the underlying RPC service, returning a future for
  the result of the callable. If the callable is not completed within the given timeout, then
  the future will be failed with a {@link TimeoutException}.
  
  @param callable Callable to be executed in the main thread of the underlying rpc server
  @param timeout Timeout for the callable to be completed
  @param <V> Return type of the callable
  @return Future for the result of the callable.