fix: Potential ThreadPool Leakage in base_session

Signed-off-by: neatguycoding <15627489+NeatGuyCoding@users.noreply.github.com>

api/core/mcp/session/base_session.py

@@ -1,7 +1,7 @@
 import logging
 import queue
 from collections.abc import Callable
-from concurrent.futures import ThreadPoolExecutor
+from concurrent.futures import Future, ThreadPoolExecutor
 from contextlib import ExitStack
 from datetime import timedelta
 from types import TracebackType
@@ -172,8 +172,8 @@ class BaseSession(
         self._in_flight = {}
         self._exit_stack = ExitStack()
         # Initialize executor and future to None for proper cleanup checks
-        self._executor = None
+        self._executor: ThreadPoolExecutor | None = None
-        self._receiver_future = None
+        self._receiver_future: Future | None = None
 
     def __enter__(self) -> Self:
         self._executor = ThreadPoolExecutor()
@@ -181,7 +181,7 @@ class BaseSession(
         return self
 
     def check_receiver_status(self) -> None:
-        if self._receiver_future.done():
+        if self._receiver_future and self._receiver_future.done():
             self._receiver_future.result()
 
     def __exit__(
@@ -200,7 +200,7 @@ class BaseSession(
 
         # Shutdown the executor
         if self._executor:
-            self._executor.shutdown(wait=True, timeout=5.0)
+            self._executor.shutdown(wait=True)
 
     def send_request(
         self,