diff --git a/github/client.py b/github/client.py
index d3b0b29..9289d0e 100644
--- a/github/client.py
+++ b/github/client.py
@@ -372,7 +372,10 @@ class GHClient:
         """:class:`float`: Returns the latency of the client."""
         return await self.http.latency()
 
+    async def close(self) -> None:
+        """Close the session."""
+        await self.http.session.close()
+
 
 class Client(GHClient):
     pass
-
diff --git a/github/http.py b/github/http.py
index 24cb6fb..e38fc82 100644
--- a/github/http.py
+++ b/github/http.py
@@ -18,6 +18,7 @@ from .exceptions import *
 from .exceptions import GistNotFound, RepositoryAlreadyExists, MissingPermissions
 from .exceptions import FileAlreadyExists
 from .exceptions import ResourceAlreadyExists
+from .exceptions import Ratelimited
 from .objects import User, Gist, Repository, File, bytes_to_b64
 from .urls import *
 from . import __version__
@@ -45,7 +46,8 @@ async def on_req_start(
 ) -> None:
     """Before-request hook to make sure we don't overrun the ratelimit."""
     # print(repr(session), repr(ctx), repr(params))
-    pass
+    if session._rates.remaining in ('0', '1'): #type: ignore
+        raise Exception('Ratelimit exceeded')
 
 
 async def on_req_end(session: aiohttp.ClientSession, ctx: SimpleNamespace, params: aiohttp.TraceRequestEndParams) -> None: