Ant, backed by Chinese e-commerce giant Alibaba Group, plans to list simultaneously in Hong Kong and Shanghai. : HONG KONG (Reuters) - Goldman Sachs has joined the growing list of investment banks working on Chinese financial technology firm Ant Group's mammoth initial public offering of up to $30 billion, two people with direct knowledge of the matter said. Ant, backed by Chinese e-commerce giant Alibaba Group <9988.HK>, plans to list simultaneously in Hong Kong and Shanghai, in what sources have said could be the world's largest IPO and come as soon as October.