Add check for Python 3.8

Author: kapkekes

fastapi_utils/cbv.py

@@ -1,4 +1,6 @@
+import functools
 import inspect
+import sys
 from typing import (
     Any,
     Callable,
@@ -16,6 +18,9 @@
 from fastapi.routing import APIRoute
 from starlette.routing import Route, WebSocketRoute
 
+if sys.version_info >= (3, 9, 0):
+    get_type_hints = functools.partial(get_type_hints, include_extras=True)
+
 PYDANTIC_VERSION = pydantic.VERSION
 if PYDANTIC_VERSION[0] == "2":
     from typing_inspect import is_classvar