I would like to mention the shuttle driver who drove the hotel shuttle to the airport at 6:30 AM on July 19. He checked my flight at the airport website in advance because it was raining with thunder and found that my flight from Madison to Chicago got canceled. Then he guided me to the counter of the American Airline in the airport and confirmed it together. In the meantime he called to the hotel and figure out the bus schedule to the Chicago airport. However, the bus was scheduled at 11 AM. To catch up the connection flight from Chicago to Seoul, Korea, he informed me that the only ways are to use a cab or a uber-like service. With his great help, I was able to find out a ride by LIFT with my friends and arrived at Chicago O'Hare airport on time for the flight to Korea without a problem.
I really appreciate his kindness and great help. If he had just dropped at the airport without any information about the cancellation, I would not have caught up the flight departing from Chicago.