Based on the issue description and traceback, I can understand the problem well enough to create the patch. The issue is:

1. `StaticFilesHandlerMixin` has a `get_response` method that serves static files
2. When using `ASGIStaticFilesHandler`, it needs a `get_response_async` method because ASGI handler calls `get_response_async`
3. The mixin is missing this async method

Looking at the traceback:
- `django/contrib/staticfiles/handlers.py:86` - ASGIStaticFilesHandler.__call__
- `django/core/handlers/asgi.py:161` - ASGIHandler.__call__ calls `get_response_async`
- `django/core/handlers/base.py:148` - BaseHandler.get_response_async calls `_middleware_chain`

The fix needs to add a `get_response_async` method to `StaticFilesHandlerMixin` that mirrors the logic of `get_response` but is async.

Based on Django's typical structure for static files handlers, here's the patch:

--- a/django/contrib/staticfiles/handlers.py
+++ b/django/contrib/staticfiles/handlers.py
@@ -1,3 +1,4 @@
+from urllib.parse import urlparse
 from urllib.request import url2pathname
 
 from django.conf import settings
@@ -43,6 +44,19 @@ class StaticFilesHandlerMixin:
             return response
         return super().get_response(request)
 
+    async def get_response_async(self, request):
+        try:
+            return await sync_to_async(self.serve, thread_sensitive=False)(request)
+        except Http404 as e:
+            return response_for_exception(request, e)
+
+    async def get_response_async(self, request):
+        if self._should_handle(request.path):
+            try:
+                return await sync_to_async(self.serve, thread_sensitive=False)(request)
+            except Http404 as e:
+                return response_for_exception(request, e)
+        return await super().get_response_async(request)
+
 
 class StaticFilesHandler(StaticFilesHandlerMixin, WSGIHandler):
     """

Wait, I need to check the exact structure. Let me think about this more carefully based on the traceback and typical Django patterns.

Looking at the traceback again:
```
File ".../src/django/django/contrib/staticfiles/handlers.py", line 86, in __call__
    return await super().__call__(scope, receive, send)
File ".../src/django/django/core/handlers/asgi.py", line 161, in __call__
    response = await self.get_response_async(request)
```

The `ASGIStaticFilesHandler` calls `super().__call__` which goes to `ASGIHandler.__call__`, which calls `self.get_response_async(request)`. The `StaticFilesHandlerMixin` only provides `get_response` but not `get_response_async`.

The fix should add `get_response_async` to `StaticFilesHandlerMixin` that mirrors the sync `get_response` method logic.

--- a/django/contrib/staticfiles/handlers.py
+++ b/django/contrib/staticfiles/handlers.py
@@ -1,4 +1,5 @@
 from urllib.request import url2pathname
 
+from asgiref.sync import sync_to_async
 from django.conf import settings
 from django.contrib.staticfiles import utils
 from django.contrib.staticfiles.views import serve
@@ -43,6 +44,13 @@ class StaticFilesHandlerMixin:
             return response
         return super().get_response(request)
 
+    async def get_response_async(self, request):
+        if self._should_handle(request.path):
+            try:
+                return await sync_to_async(self.serve, thread_sensitive=False)(request)
+            except Http404 as e:
+                return response_for_exception(request, e)
+        return await super().get_response_async(request)
+
 
 class StaticFilesHandler(StaticFilesHandlerMixin, WSGIHandler):
     """