Looking back at the checklists we made for 2017, I think it is pretty interesting to see how you all progress :) In hindsight, it's quite sad that I did not write one myself...
Since the beginning of 2017 (and probably a bit longer than that), I have been dedicating time to learning Rust and how to work with ECSs in order to write games with future-tech from scratch. (By the way, I decided to use the Amethyst data-driven game engine for that purpose)
Also, I've been fiddling a bit more with functional programming in JS lately (mainly getting to know how Fantasy-Land and Static-Land fit into the JS world) and what I can learn from it. One result of that is, that my application host is getting a brand new architecture, which will improve modularity as well as usage for all kinds of data-oriented problems (not just as web server).
Well, I also like to combine what I learned, so I created two NodeJS modules: result-js and roption-js, which implement the Rust Result and Option interfaces. I will use them in future projects (and re-writes), since I really love the safety I get from them.
Last but not least, I am a University student of Applied IT Security, so I learned a lot about different ciphers, how they work internally, how secure they are, how to break them, etc. It is quite interesting, however very theoretical with not that much "application". I hope to use that knowledge to improve my current projects.
From here, I would also love to dabble a bit at Kotlin, however I do not see any immediate use-case for me, so I will probably postpone it further.