add threads

[shimondoodkin]

I could not use global variables, GIL is ok.

[shimondoodkin]

if there is merge conflict: final result example: https://github.com/shimondoodkin/zero/blob/main/zero/server.py#L106-L111

[Ananto30]

@shimondoodkin would you mind adjusting your pr with the conflict? :pray: I would like to use a thread pool.