add Visitor in example

examples/common.py

@@ -0,0 +1,12 @@
+from starlette.requests import Request
+
+
+def get_client_ip(request: Request):
+    """
+    :param request:
+    :return:
+    """
+    forwarded = request.headers.get("X-Forwarded-For")
+    if forwarded:
+        return forwarded.split(",")[0]
+    return request.client.host