parsing result in io thread, and signal worker with full result

[Xudong-Huang]

1. do io in the same thread
2. no need to use slow channel rx
3. reduce context switch significantly

[casibbald]

I learned this the hard way!

https://medium.com/@casibbald/building-lifeguard-a-parallel-universe-orm-for-rust-coroutines-95682da3cfbf