This is very cool. I'd be interested to see more data interaction and how to call a Go function from Rust.

I implemented a similar experiment with Haskell and Rust[0]. It does some simple math and also passes a Haskell callback function into Rust code. Unfortunately, I think we lose quite a bit of information by passing through C code (e.g. Rust's parametric polymorphism).

[0] - https://github.com/creichert/haskellrustdemo (Careful, it will not compile with rust 1.0 beta (use of unstable library feature 'libc')).