How to persist elements in the Flask g context

Solution
from flask import Flask, g, current_app

def create_app():
    app = Flask(__name__)
    with app.app_context():
        #in context, you can use current_app to fetch or assign app.config['key']
        current_app.bb = 'bbb!' # not normally used
        current_app.config['aaa'] = 'aaa!' # usually we use current_app.config['name'] = 'value'
        print("1", app.bb) # for this example, using app or current_app has no different.
        print("1", current_app.config['aaa'])

    with app.app_context():
        #here to use current_app to get what you want.
        print("2", current_app.bb)
        print("2", current_app.config['aaa'])

>>>create_app()
1 bbb!
1 aaa!
2 bbb!
2 aaa!
from flask import Blueprint, current_app

...

my_routes = Blueprint("my_routes", __name__)

...


@my_routes.route("/foo_path", methods=["POST"])
def foo_route():
    ...
    my_aaa = current_app.config["aaa"]
import atexit

def _close_resources(app):
    with app.app_context():
        app.logger.warning("Closing resources")
        current_app.config["aaa_resource"].close()

...

def create_app():

    app = Flask(__name__)

    def app_close_resources():
        return _close_resources(app)

    atexit.register(app_close_resources)
    ...