Avoid closing multiple times

Author: Pil0tXia

eventmesh-sdks/eventmesh-sdk-java/src/main/java/org/apache/eventmesh/client/grpc/consumer/SubStreamHandler.java

@@ -40,6 +40,8 @@ public class SubStreamHandler<T> extends Thread implements Serializable {
 
     private final transient CountDownLatch latch = new CountDownLatch(1);
 
+    private volatile boolean isClosed = false;
+
     private final transient ConsumerServiceStub consumerAsyncClient;
 
     private final transient EventMeshGrpcClientConfig clientConfig;
@@ -130,6 +132,12 @@ public void run() {
     }
 
     public void close() {
+        // Avoid closing multiple times
+        if (isClosed) {
+            return;
+        }
+        isClosed = true;
+
         if (this.sender != null) {
             senderOnComplete();
         }