Ask HN: How to become a better coder?

I've been a software engineer for over a decade, worked at startups and established companies and built a variety of systems at scale - frontend, backend, db and client. I consider myself quite technical and a quick learner, and able to pick up pretty much anything I apply myself towards.

I recently I interviewed at Amazon, Facebook and Google. I received and accepted an offer from Amazon. The other two declined and basically gave me the same feedback - that I had excellent communication and design skills, but had to improve my coding.

I consider myself a good coder, but I would like to take this as constructive criticism and actually improve on my craft.

So, question is - how would I go about doing this in a structured, planned manner? I realize this is a never ending process, but I would like to incrementally improve over, say, the next 12 months. I have a family and other obligations, so would probably prefer something that could be consumed in reasonable doses.