[phonebucket]

I don't see the two as directly comparible.

Go is garbage collected, Rust is not. Go is compact, Rust has lots of functional programming bells and whistles like algebraic data types. Go compiles quickly, Rust takes a while. Go has first class support for concurrency, Rust does not.

Roll with whichever you like. For me, as a side-language, it's Go, because I already enjoy and use Haskell, and I feel like Go contrasts more with Haskell. If I didn't know Haskell, I'd probably choose Rust.

If it wasn't for a side-language, but was for a specific project, I'd choose on the basis of available libraries.