Bullet train D5599 leaves from Hangzhou at 19:53 and pass Shangyu. It takes a hour from Hangzhou to Shangyu. This is the fastest way and you should take airport bus to Hangzhou Railway Station first. Buses are not avalable after 18:30. So, you should try to get the train. If you miss the last train, find a budget inn to stay one night in Hangzhou. It will be not easy to find a taxi to Shangyu, which is expensive either.