Trouble Obtaining Auth Token from Upwork API Python

Question

I have an Upwork API associated with my account, and I'm trying to use it for messaging purposes. I am following the API reference documentation. I have both the consumer and secret keys.

However, I'm encountering an issue that I am making a call to the callback endpoint to receive the auth_token necessary to proceed further, but I am not receiving it as expected.

Could someone please help me identify and resolve this issue?

main.py

from flask import Flask, request
import upwork

app = Flask(__name__)

config = upwork.Config({
    "consumer_key": "xxxxxxx",
    "consumer_secret": "xxxxxxx",
    "redirect_uri": "https://localhost"
})


@app.route('/callback')
def callback():
    # Get the authorization code from the request
    auth_code = request.args.get('code')
    client = upwork.Client(config)
    token = client.get_authorization_url()
    # print("Authorization URL:", token)
    return f"Authorization URL:{token}"


if __name__ == '__main__':
    app.run(host='localhost', port=5000)

calling the callback as:

test.py

import requests

response = requests.get("http://localhost:5000/callback")

getting this in return:

Authorization URL:https://www.upwork.com/services/api/auth?oauth_token=None

I am expecting it to return the auth_token so that I can proceed further with it.