Rust has been the most surprisingly fun thing I learned this year. I was shocked at how quickly I was productive (even while still having no idea what I was doing). It really is astonishingly like using a very high level language, with a few weird quirks.

I'm really looking forward to building something bigger with it in 2019. I don't know what it'll be yet, but it was such a satisfying experience working with a low-level language (which I haven't done in 15 years, or so), and having it be really pleasant. I think it's impossible to overstate how important having a good way to easily install libraries/modules/whatever is, and Cargo gets it right in ways that few systems languages ever have (that I'm aware of, anyway).