title: using an enviroment variable for local sequelize configuration
body: <p>I'm looking to use an environment variable inside of the config.json file of my project using sequelize. I'm using dotenv to set environment variables locally. My config.json file looks like this</p>
  
  <pre><code>{
    "development": {
      "username": process.env.DB_USER,
      "password": process.env.DB_PASS,
      "database": process.env.DB_DATABASE,
      "host": process.env.DB_HOST,
      "dialect": "mysql"
    },
    "test": {
      "username": "root",
      "password": null,
      "database": "database_test",
      "host": "127.0.0.1",
      "dialect": "mysql"
    },
    "production": {
      "use_env_variable": "JAWSDB_URL",
      "dialect": "mysql"
    }
  }
  </code></pre>
  
  <p>The issue I'm having is that I can't use variables inside the config.json file. It looks like for production I can use the "use_env_varable" key and use the env variable for my connection string. So I guess I either need a way to figure out the combined connection string for my local mysql db or a way to use variables inside the config.json. Any solutions?</p>