task: metadata: install: pip install -e .[full]
patch: diff --git a/docs/websockets.md b/docs/websockets.md
index 43406ac..1128bce 100644
--- a/docs/websockets.md
+++ b/docs/websockets.md
@@ -75,7 +75,7 @@ Use `websocket.receive_json(data, mode="binary")` to receive JSON over binary da
 
 ### Closing the connection
 
-* `await websocket.close(code=1000)`
+* `await websocket.close(code=1000, reason=None)`
 
 ### Sending and receiving messages
 
diff --git a/starlette/websockets.py b/starlette/websockets.py
index bf4cca8..da74060 100644
--- a/starlette/websockets.py
+++ b/starlette/websockets.py
@@ -13,8 +13,9 @@ class WebSocketState(enum.Enum):
 
 
 class WebSocketDisconnect(Exception):
-    def __init__(self, code: int = 1000) -> None:
+    def __init__(self, code: int = 1000, reason: str = None) -> None:
         self.code = code
+        self.reason = reason or ""
 
 
 class WebSocket(HTTPConnection):
@@ -146,13 +147,18 @@ class WebSocket(HTTPConnection):
         else:
             await self.send({"type": "websocket.send", "bytes": text.encode("utf-8")})
 
-    async def close(self, code: int = 1000) -> None:
-        await self.send({"type": "websocket.close", "code": code})
+    async def close(self, code: int = 1000, reason: str = None) -> None:
+        await self.send(
+            {"type": "websocket.close", "code": code, "reason": reason or ""}
+        )
 
 
 class WebSocketClose:
-    def __init__(self, code: int = 1000) -> None:
+    def __init__(self, code: int = 1000, reason: str = None) -> None:
         self.code = code
+        self.reason = reason or ""
 
     async def __call__(self, scope: Scope, receive: Receive, send: Send) -> None:
-        await send({"type": "websocket.close", "code": self.code})
+        await send(
+            {"type": "websocket.close", "code": self.code, "reason": self.reason}
+        )

problem_statement: [Feature] Reason for websocket.close
I've recently started actively developing with websockets in starlette. When closing a websocket you can provide a code e.g. 1000, 1008 … to tell the client the basic reason. But the websocket protocol allows the developer to also give UTF-8-encoded data as a complementary description/ reason. This would be useful in multiple cases such as mentioning the specific violitioan for code 1008 (POLICY VIOLIATION). [Websockets](https://websockets.readthedocs.io/en/stable/api.html?highlight=reason#websockets.protocol.WebSocketCommonProtocol.close) supports this too and their [implementation](https://websockets.readthedocs.io/en/stable/_modules/websockets/protocol.html#WebSocketCommonProtocol.close) could maybe help.

Specification: [https://tools.ietf.org/](https://tools.ietf.org/html/rfc6455#section-5.5.1)


repo: encode/starlette
test_cmd: pytest --no-header -rA --tb=line --color=no -p no:cacheprovider -W ignore::DeprecationWarning
test_patch: diff --git a/starlette/testclient.py b/starlette/testclient.py
index 0b4bc78..c951767 100644
--- a/starlette/testclient.py
+++ b/starlette/testclient.py
@@ -352,7 +352,9 @@ class WebSocketTestSession:
 
     def _raise_on_close(self, message: Message) -> None:
         if message["type"] == "websocket.close":
-            raise WebSocketDisconnect(message.get("code", 1000))
+            raise WebSocketDisconnect(
+                message.get("code", 1000), message.get("reason", "")
+            )
 
     def send(self, message: Message) -> None:
         self._receive_queue.put(message)
diff --git a/tests/test_websockets.py b/tests/test_websockets.py
index f3242d1..b11685c 100644
--- a/tests/test_websockets.py
+++ b/tests/test_websockets.py
@@ -405,3 +405,20 @@ def test_websocket_scope_interface():
     assert websocket == websocket
     assert websocket in {websocket}
     assert {websocket} == {websocket}
+
+
+def test_websocket_close_reason(test_client_factory) -> None:
+    def app(scope):
+        async def asgi(receive, send):
+            websocket = WebSocket(scope, receive=receive, send=send)
+            await websocket.accept()
+            await websocket.close(code=status.WS_1001_GOING_AWAY, reason="Going Away")
+
+        return asgi
+
+    client = test_client_factory(app)
+    with client.websocket_connect("/") as websocket:
+        with pytest.raises(WebSocketDisconnect) as exc:
+            websocket.receive_text()
+        assert exc.value.code == status.WS_1001_GOING_AWAY
+        assert exc.value.reason == "Going Away"