I was in a very similar situation after I spent decades working as an executive totally forgetting my tech skills I had when I was young. Before I reached 20 I wrote an heavy ERP system and few years ago I was even afraid to touch the shell of a bare metal server (which is btw fun and very satisfying, once you got into it you literally feel the power).

Since I love tech and programming I wanted to get back, not to find a tech job or run a tech startup, no I just wanted something to distract myself after work. So I began dipping into random languages, libs & frameworks. Bought books, read tutorial and did crash courses. I chose popular and new tech, stuff that matters and things which frequently pop up on HN. From mobile development over functional languages to the hottest JS front-end libs. I played around but usually after a few days I lost quickly any interest, I didn't know why.

Eventually I found the best way get back again and it's easy: Look for a real problem you have yourself and you want to solve. Just for yourself, just to use it yourself. Once you identified the problem you search for the right tool and everything else comes by itself and before you realize you mastered a heavy language/framework in a few days/weeks.

Without a concrete mission which really must matter to you all efforts to get into any appealing tech such as Swift, ES6, react-redux, Android dev, Go will feel shallow and you'll end up wasting time going through tutorials/books/guides questioning your journey.