AckCallback.onTimeout should be invoked during shutdown state

src/main/java/com/corundumstudio/socketio/ack/AckManager.java

@@ -172,6 +172,10 @@ public class AckManager implements Disconnectable {
 
         Set<Long> indexes = e.getAckIndexes();
         for (Long index : indexes) {
+            AckCallback<?> callback = e.getAckCallback(index);
+            if (callback != null) {
+                callback.onTimeout();
+            }
             SchedulerKey key = new AckSchedulerKey(Type.ACK_TIMEOUT, client.getSessionId(), index);
             scheduler.cancel(key);
         }

src/main/java/com/corundumstudio/socketio/transport/NamespaceClient.java

@@ -104,6 +104,7 @@ public class NamespaceClient implements SocketIOClient {
     @Override
     public void send(Packet packet, AckCallback<?> ackCallback) {
         if (!isConnected()) {
+            ackCallback.onTimeout();
             return;
         }
         long index = baseClient.getAckManager().registerAck(getSessionId(), ackCallback);