Kudos! I'm looking forward to following your progress. For clarity, in the title you might want to change 'Cocoa' to 'macOS'. Cocoa is a marketing term that was used back in the day but I suspect many people have never heard of it.
Do we have a repo like <a href="https://github.com/gothinkster/realworld" rel="nofollow">https://github.com/gothinkster/realworld</a> but for HN clients?