No application module specified deploying flask app

Hello, i must say this is my first project. Now I built a flask app, that uses a image classifier. the flask integration works fine locally, but i would like to deploy the app to a lager audience.

i followed the deployment strategy proposed on this git https://github.com/digitalocean/sample-flask.git but i get the following error:

number-reader | 12:12:52 usage: gunicorn [OPTIONS] [APP_MODULE] number-reader | 12:12:52 gunicorn: error: No application module specified.

app = Flask(__name__)

# To setup Bootstrap templates
Bootstrap(app)

# Load trained model
with open("model/classifier.pickle", "rb") as handle:
    classifier = pickle.load(handle)


@app.route('/', methods=['GET', 'POST'])
def load_image():
    if request.method == 'POST':
if __name__ == '__main__':
    app.run(debug=True)