[Flask] エラー"RuntimeError: Working outside of request context."について

前提

Flaskで非同期処理を実行するAPIシステムを作っています。
@app.route()からclassで定義した関数に引数を渡そうとした時に以下のエラーメッセージが発生しました。

実現したいこと

@app.route()からclassで定義した関数に引数（session['text']）を渡せるようにする。

発生している問題・エラーメッセージ

127.0.0.1 - - [08/May/2022 15:13:13] "GET / HTTP/1.1" 200 -
Exception in thread Thread-8:
Traceback (most recent call last):
  File "/Users/admin/.pyenv/versions/3.9.7/lib/python3.9/threading.py", line 973, in _bootstrap_inner
    self.run()
  File "/Users/admin/Documents/Python/Flask_Oauth-master/test3.py", line 25, in run
    print(session['text'])
  File "/Users/admin/.pyenv/versions/3.9.7/lib/python3.9/site-packages/werkzeug/local.py", line 422, in __get__
    obj = instance._get_current_object()
  File "/Users/admin/.pyenv/versions/3.9.7/lib/python3.9/site-packages/werkzeug/local.py", line 544, in _get_current_object
127.0.0.1 - - [08/May/2022 15:13:13] "GET /?__debugger__=yes&cmd=resource&f=style.css HTTP/1.1" 200 -
127.0.0.1 - - [08/May/2022 15:13:13] "GET /?__debugger__=yes&cmd=resource&f=console.png HTTP/1.1" 200 -
127.0.0.1 - - [08/May/2022 15:13:13] "GET /?__debugger__=yes&cmd=resource&f=ubuntu.ttf HTTP/1.1" 200 -
    return self.__local()  # type: ignore
  File "/Users/admin/.pyenv/versions/3.9.7/lib/python3.9/site-packages/flask/globals.py", line 33, in _lookup_req_object
127.0.0.1 - - [08/May/2022 15:13:13] "GET /?__debugger__=yes&cmd=resource&f=debugger.js HTTP/1.1" 200 -
    raise RuntimeError(_request_ctx_err_msg)
RuntimeError: Working outside of request context.

This typically means that you attempted to use functionality that needed
an active HTTP request.  Consult the documentation on testing for
information about how to avoid this problem.

該当のソースコード

Python
1from flask import Flask, render_template, session ,make_response,request
2import sched,time,threading
3from time import sleep
4
5app = Flask(__name__)
6app.secret_key = 'hogehoge'
7
8class MyThread(threading.Thread):
9    def __init__(self):
10        super(MyThread, self).__init__()
11        self.stop_event = threading.Event()
12
13    def stop2(self):
14        self.stop_event.set()
15
16    def run(self):
17        try:
18            for _ in range(1000):
19                print(session['text'])
20                time.sleep(3)
21                # 定期的にフラグを確認して停止させる
22                if self.stop_event.is_set():
23                    break
24        finally:
25            print('時間のかかる処理が終わりました\n')
26
27@app.route('/')
28def admin():
29    with app.test_request_context():
30        session['text'] = "成功"
31        t = MyThread()
32        t.start()
33    return make_response("出力成功")
34
35app.run(debug=True, host='localhost', port=3000, threaded=True)