Oh nice! Yeah this is basically the same design/intuition that this project also started out with (I also just wanted some way to combine the benefits of aria2c with piping). Wish I found this earlier lol.

I only later decided to look into also parallelizing the tar extraction as well. This originally started with looking into making a change to the GNU tar source code itself. However upon cloning I realized there were a lot of design choices in tar that made the assumption of single threaded execution (global state, etc). At this point I decided it would just be easier to re-implement the tar extraction myself using golang's "archive/tar" package.