DoorDash (DASH) stock rose 13% during premarket hours on Thursday after announcing on Wednesday that its revenue rose 38% in the fourth quarter as it gained new U.S. customers and added new services like restaurant reservations. But the San Francisco-based delivery company also warned of costly investments ahead. DoorDash CEO and Co-founder Tony Xu said DoorDash is in the midst of building a single tech platform that will bring together its many international businesses. DoorDash bought Wolt, a Finnish de ...