code: private ManagedChannel getNextChannel() {
      int currentRequestNum = requestCount.getAndIncrement();
      int index = Math.abs(currentRequestNum % channels.size());
      return channels.get(index);
    }
docs: Performs a simple round robin on the list of {@link ManagedChannel}s in the {@code channels}
  list. This method should not be synchronized, if possible, to reduce bottlenecks.
  
  @return A {@link ManagedChannel} that can be used for a single RPC call.