I've been keeping an eye on the ShipBuilder PAAS project - the minimalist Heroku clone written in Go. It is starting to look quite promising.

Quoting jaytaylor's comment [1] from below:

    > You may be interested in checking out ShipBuilder - it
    > is an open-source Heroku-clone PaaS.
    >
    > ShipBuilder is written in Go, and uses Git, LXC and
    > HAProxy to deliver a complete solution for
    > an application platform-as-a-service.
    >
    > http://shipbuilder.io [2]
    >
    > https://github.com/sendhub/shipbuilder [3]

[1] https://news.ycombinator.com/item?id=6292463

[2] http://shipbuilder.io

[3] https://github.com/sendhub/shipbuilder