Which language or framework to pair with a Swift app?

Since a few of us seem to be interested in learning Swift, I wondered what languages or frameworks people are (or thinking about) pairing a Swift app with on the backend?

Are you sticking with something like Rails or Phoenix? Or opting to use one of Swift’s own frameworks, like Vapor or Kitura?

I wonder also if learning a Swift web framework might actually be a good way to learn Swift - since many of us are familiar with the workings of a framework and it might help us get our head around things?..