[Vlasenko Fedor]

"sequelize": "^6.3.5"
server.js

const {sequelize} = require('./models/index');
async function databaseConnection() {
    console.log(`Checking database connection...`);
    try {
        await sequelize.authenticate();
        //await sequelize.sync({ force: true });
        console.log('Database connection OK!');
    } catch (error) {
        console.log('Unable to connect to the database:');
        console.log(error.message);
        process.exit(1);
    }
}

async function init() {
    await databaseConnection();
    app.listen(3000, err => {
        if (err) {
            console.log('============================ERROR============================');
            console.log(err);
            console.log('============================ERROR============================');
            throw err
        }
        console.log(`server listening on ${app.server.address().port}`)
    });
//..............................
}
init();

/models/index.js

'use strict';

const fs = require('fs');
const path = require('path');
const Sequelize = require('sequelize');
const env = process.env.NODE_ENV || 'development';
const config = require(__dirname + '/../config/config.json')[env];
const db = {};

let sequelize;
if (config.use_env_variable) {
    sequelize = new Sequelize(process.env[config.use_env_variable], config);
} else {
    sequelize = new Sequelize(config.database, config.username, config.password, config);
}

fs
    .readdirSync(__dirname)
    .forEach(file => {
        if (file.indexOf('.') !== 0 && file.slice(-8) === 'Model.js') {

            try {
                const model = require(path.join(__dirname, file))(sequelize, Sequelize.DataTypes);
                db[model.name] = model;
            } catch (e) {
                console.log('================ERROR====================');
                console.log(path.join(__dirname, file));
                console.log(e);
                console.log('===========================================');
            }

        }
    });

Object.keys(db).forEach(modelName => {
    if (db[modelName].associate) {
        db[modelName].associate(db);
    }
});

db.sequelize = sequelize;
db.Sequelize = Sequelize;

module.exports = db;

это пример с рабочего проекта