Bot started but /start command isn’t doing anything

After setting up the python teegram bot script on Heroku using docker container, script is running but the /start command isn’t doing anything at all

Setting up Telegram bot on Heroku server using Python telegram bot

import logging
import os
import sys
from telegram.ext import Updater, CommandHandler

logging.basicConfig(format='%(asctime)s - %(name)s - %(levelname)s - %(message)s',level=logging.INFO)
logger = logging.getLogger()

# Get mode and token from environment
mode = os.getenv("MODE")
TOKEN = os.getenv("TOKEN")

if mode == "prod":
    def run(updater):
        PORT = int(os.environ.get("PORT", "8443"))
        AppName = os.environ.get("AppName")
        # Code from https://github.com/python-telegram-bot/python-telegram-bot/wiki/Webhooks#heroku
        updater.start_webhook(listen="0.0.0.0",
                              port=PORT,
                              url_path=TOKEN)
        updater.bot.set_webhook("https://{}.herokuapp.com/{}".format(AppName, TOKEN))
else:
    logger.error("No mode specified")
    sys.exit(1)

def start(update, context):
    logging.info("User started bot {}".format(update.message.from_user.first_name))
    context.bot.send_message(chat_id=update.message.chat_id, text="Your name is {}".format(update.message.from_user.first_name))


if __name__ == '__main__':
    logger.info("Bot started")
    updater = Updater(token=TOKEN, use_context=True)

    # ADD dispatcher with command handler
    dispatcher = updater.dispatcher
    logger.info("working till here")
    start_handler = CommandHandler('start', start)
    dispatcher.add_handler(start_handler)
    logger.info(dispatcher.add_handler(start_handler))
    run(updater)

Expect the /start command print user name but not working

Source: StackOverflow