update: 更新程序，增加了并发测试程序

tests/unit_test/concurrent_chat_test.py

@@ -0,0 +1,12 @@
+from chat_test import chat_test
+import multiprocessing
+
+if __name__ == '__main__':
+    processes = []
+    for _ in range(2):
+        p = multiprocessing.Process(target=chat_test)
+        processes.append(p)
+        p.start()
+    
+    for p in processes:
+        p.join()