In rare cases, your side project is addressing one of the businesses needs directly, giving you domain knowledge. More likely is that it does not. At this point, the value-add of that project is that is improves your understanding of the techs you used. Can you talk about the pros and cons of using Go/React/Angular 2/techBuzzwordDuJour? That speaks to your passion and creativity, and stands to improves the knowledgeable of the team that hires you.
tl;dr: Do something fun that you enjoy. The rest takes care of itself.