database.py

from gino import Gino

db = Gino()


async def start():
    await db.set_bind('postgresql://localhost/gino')

    # Create tables
    await db.gino.create_all()

main.py

import database
# you must import all models for them to appear in the metadata
from models import *

# blabla

async def on_startup(_):
    await database.start()

start_webhook(..., on_startup=on_startup)

middlewares.py

from aiogram.dispatcher.middlewares import BaseMiddleware
from aiogram import types

from models import User


class MetricMiddleware(BaseMiddleware):
    async def on_process_message(self, message: types.Message, data: dict):
        user = await User.get_or_create(message.from_user.id)
        await user.up_messages()
        data["user"] = user

some_handlers_file.py

from aiogram import types

from models import User


@dp.message_handler(commands=['count'])
async def test(message: types.Message, user: User):
    await message.answer(f"The bot has processed {user.messages} messages from you.")

user.py

# As planned, this file is located in the "models" directory.

from database import db


class User(db.Model):
    __tablename__ = 'users'

    id: int = db.Column(db.Integer(), primary_key=True)
    messages: int = db.Column(db.Integer(), default=0)
    
    @classmethod
    async def get_or_create(cls, id) -> "User":
        user = await cls.get(id)
        
        if user is None:
            return await cls.create(id=id)
        return user
    
    async def up_messages(self) -> int:
        """
        Update the statistics of the messages.
        
        Return the updated value.
        """
        await self.update(messages=self.messages+1).apply()
        return self.messages