I was rather surprised that Microsoft didn't announce any USB-C dongles alongside Surface Go. Surprise: They re coming.
Two Surface-branded USB-C dongles are currently available for pre-order at Best Buy, a U.S.-based electronics retailer. They are:
Microsoft Surface USB-C to Ethernet and USB Adapter. This $55 adapter is compatible with all Surface models with built-in USB-C port (e.g. Surface Book 2 and Surface Go) and provides both a full-sized USB-A port and a 1 Gbps Ethernet port.
Microsoft Surface USB-C-to-USB Adapter. This $20 adapter is likewise Compatible with all Surface models with a built-in USB C port and provides a single full-sized USB-A port.
Note, too, that any USB-C adapter or dongle will work just fine with Surface Go. You don't need the Microsoft ones.