Learn or ship

I've often found myself in the situation where I had to write some code and was stuck at the first question; what language am I going to write this in?

Writing new code is always an opportunity to try out something fresh — a new programming language, a new framework or library, new infrastructure provider, ... Many of my side projects have stalled before completion because I answered that first question incorrectly.

Actually, answering it is fairly straightforward: What is your project's primary goal? Do you want to ship it or learn something new? It's important not to confuse these objectives.

If you need to finish the project you're starting, then use what you already know and what will help you achieve that goal. You can always iterate later. If finishing the project isn't the primary goal, feel free to explore something new and learn along the way.

The reverse question is also worth considering: If you want to try something new, what should you write? Start with something small and non-critical. You might rewrite a small existing script in that new language or tackle a coding challenge, like Advent of Code.