При запуске бота, вылазит ошибка Process finished with exit code 0

from aiogram import Bot, Dispatcher
from aiogram.types import Message
from aiogram.filters import CommandStart


async def main():
dp = Dispatcher()
bot = Bot(token="токен скрыт")
await dp.start_polling(bot)


@router.message(CommandStart())
async def mess(message: Message):
await message.answer("Hi")