Goyang Sports Complex: the last train after the show, and what happens when it rains

The nearest station is Daehwa on Line 3, about a 7-minute walk. Weekday last trains: 24:03 toward Yaksu (reaches central Seoul) and 24:36 toward Samsong (stops outside Seoul). Weekends: 23:03 toward Yaksu and 23:36 toward Samsong.
24:36 means 00:36 the next night. And the 24:36 train is labeled toward Ogeum but only runs to Samsong. To reach central Seoul you need the 24:03, or 23:03 on a weekend.
It is an open-air stadium with no roof. If it rains you get rained on, and umbrellas are usually refused at the door. Bring a poncho.
If the show is on a weekend, the weekend times are the ones that count. With a long encore, 23:03 arrives sooner than you think.