My few encounters with Go were pleasant and I stick to the idea that it is a good language.
Declaring preconditions, postconditions, and invariants, and actually checking them at runtime are two different things.
Ada's concurrency facility (tasks) reminds me of Erlang's concurrency facility. I am not fluent in any of these two languages but I like them — Ada is a fresh new entry in the list: seen a bit of it ages ago and I thought to dislike it. Now I'm looking into it again and a litte bit deeper, and I started to like it…