Ask HN: Sugesst me some pet projects

I am learning a new language (Go) for my work and I liked in the first week I was given to make a chat server to get familiar with it. I enjoyed working on that.

I am looking for similar projects which are not too easy but not too challenging either (like making a text editor). And I also want to work on something I would use rather than just build it and park it.

Looking for some ideas from the community or I want to know what are you working on.