This alludes to the fact that you can do this within the same process, simply by running goroutines and communicating over Go channels. Later, when you actually need to scale, your services already support the interface necessary to be exposed over unix sockets, websocket or spdy/tls: you just need to change the plumbing.
1: We plan on porting libswarm to every major language.
2: The idea is to use socket passing, so you can use libswarm for service discovery. Place your postgres service behind a libswarm proxy, which implements the "connect" verb: that allows a client to use libswarm for discovery.
To do this we take advantage of a low-level communication library called libchan: https://github.com/docker/libchan