Reconfigure.io projects are coded entirely in Go. We support a subset of the Go language to ensure compatibility with our compiler. I’ve just added a section to our documentation detailing which features we currently support, you can check it out here. It follows the Go spec, which provides more information on each feature.
We’re always working to expand the features we provide – if there’s something you’d really like to see, head over to our wish list and let us know!