log when channel not shutdown.

Author: rmehta19

s2a/src/main/java/io/grpc/s2a/channel/S2AHandshakerServiceChannel.java

@@ -30,6 +30,8 @@
 import io.grpc.internal.SharedResourceHolder.Resource;
 import io.grpc.netty.NettyChannelBuilder;
 import java.time.Duration;
+import java.util.logging.Level;
+import java.util.logging.Logger;
 import java.util.Optional;
 import java.util.concurrent.ConcurrentMap;
 import javax.annotation.concurrent.ThreadSafe;
@@ -132,6 +134,7 @@ public String toString() {
    */
   @VisibleForTesting
   static class HandshakerServiceChannel extends Channel {
+    private static final Logger logger = Logger.getLogger(S2AStub.class.getName());
     private final ManagedChannel delegate;
 
     static HandshakerServiceChannel create(ManagedChannel delegate) {
@@ -166,6 +169,7 @@ public void close() {
         delegate.awaitTermination(CHANNEL_SHUTDOWN_TIMEOUT.getSeconds(), SECONDS);
       } catch (InterruptedException e) {
         Thread.currentThread().interrupt();
+        logger.log(Level.WARNING, "Channel to S2A was not shutdown.");
       }
     }
   }