'No application found. Either work inside a view function or push an application context.'

I'm trying to separate my Flask-SQLAlchemy models into separate files. When I try to run db.create_all() I get No application found. Either work inside a view function or push an application context.

shared/db.py:

from flask_sqlalchemy import SQLAlchemy

db = SQLAlchemy()

app.py:

from flask import Flask
from flask_sqlalchemy import SQLAlchemy
from shared.db import db

app = Flask(__name__)
app.config['SQLALCHEMY_DATABASE_URI'] = 'My connection string'
db.init_app(app)

user.py:

from shared.db import db

class User(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    email_address = db.Column(db.String(300), unique=True, nullable=False)
    password = db.Column(db.Text, nullable=False)

Use with app.app_context() to push an application context when creating the tables.

app = Flask(__name__)
app.config['SQLALCHEMY_DATABASE_URI'] = 'My connection string'
db.init_app(app)

with app.app_context():
    db.create_all()