alts: provide channel type to HandshakerServiceChannel to suppress warning
diff --git a/alts/src/main/java/io/grpc/alts/HandshakerServiceChannel.java b/alts/src/main/java/io/grpc/alts/HandshakerServiceChannel.java
index 2f669d3..169afe3 100644
--- a/alts/src/main/java/io/grpc/alts/HandshakerServiceChannel.java
+++ b/alts/src/main/java/io/grpc/alts/HandshakerServiceChannel.java
@@ -25,6 +25,7 @@
 import io.grpc.netty.NettyChannelBuilder;
 import io.netty.channel.EventLoopGroup;
 import io.netty.channel.nio.NioEventLoopGroup;
+import io.netty.channel.socket.nio.NioSocketChannel;
 import io.netty.util.concurrent.DefaultThreadFactory;
 import java.util.concurrent.TimeUnit;
 
@@ -56,6 +57,7 @@
       EventLoopGroup eventGroup =
           new NioEventLoopGroup(1, new DefaultThreadFactory("handshaker pool", true));
       ManagedChannel channel = NettyChannelBuilder.forTarget(target)
+          .channelType(NioSocketChannel.class)
           .directExecutor()
           .eventLoopGroup(eventGroup)
           .usePlaintext()