Do you guys know about https://chatango.com ? It's a more mature product, also based on Go backend. Founder here, so please ask any questions.
The documentation on dropinchat.com mentions "groups" as a set of users which are allowed to see one another and message back and forth. Our team thinks this use case might be helpful, for example, for a website administrator to limiting communication between members on a given organizational team or individuals in a certain building, etc.
Also joined 2 mins ago.