Implement slow-mode polling (If need to save ordering of updates)

aiogram/dispatcher/dispatcher.py

@@ -142,17 +142,24 @@ class Dispatcher:
             updates = await self.bot.get_updates(offset=self.last_update_id + 1, timeout=1)
         return total
 
-    async def process_updates(self, updates):
+    async def process_updates(self, updates, fast: typing.Optional[bool] = True):
         """
         Process list of updates
 
         :param updates:
+        :param fast:
         :return:
         """
-        tasks = []
+        if fast:
+            tasks = []
+            for update in updates:
+                tasks.append(self.updates_handler.notify(update))
+            return await asyncio.gather(*tasks)
+
+        results = []
         for update in updates:
-            tasks.append(self.updates_handler.notify(update))
-        return await asyncio.gather(*tasks)
+            results.append(await self.updates_handler.notify(update))
+        return results
 
     async def process_update(self, update: types.Update):
         """
@@ -216,7 +223,8 @@ class Dispatcher:
 
         return await self.bot.delete_webhook()
 
-    async def start_polling(self, timeout=20, relax=0.1, limit=None, reset_webhook=None):
+    async def start_polling(self, timeout=20, relax=0.1, limit=None, reset_webhook=None,
+                            fast: typing.Optional[bool] = True):
         """
         Start long-polling
 
@@ -224,6 +232,7 @@ class Dispatcher:
         :param relax:
         :param limit:
         :param reset_webhook:
+        :param fast:
         :return:
         """
         if self._polling:
@@ -255,7 +264,7 @@ class Dispatcher:
                     log.debug(f"Received {len(updates)} updates.")
                     offset = updates[-1].update_id + 1
 
-                    self.loop.create_task(self._process_polling_updates(updates))
+                    self.loop.create_task(self._process_polling_updates(updates, fast))
 
                 if relax:
                     await asyncio.sleep(relax)
@@ -263,14 +272,15 @@ class Dispatcher:
             self._close_waiter._set_result(None)
             log.warning('Polling is stopped.')
 
-    async def _process_polling_updates(self, updates):
+    async def _process_polling_updates(self, updates, fast: typing.Optional[bool] = True):
         """
         Process updates received from long-polling.
 
         :param updates: list of updates.
+        :param fast:
         """
         need_to_call = []
-        for responses in itertools.chain.from_iterable(await self.process_updates(updates)):
+        for responses in itertools.chain.from_iterable(await self.process_updates(updates, fast)):
             for response in responses:
                 if not isinstance(response, BaseResponse):
                     continue