Hello!
Recently I wrote a Nginx C module called lua-io-nginx-moudle,
it provides some file APIs like the Lua I/O library. But these APIs are 100% nonblocking,
and I implemented them through the Nginx's thread pool.
Repo link:https://github.com/tokers/lua-io-nginx-module
I didn't do the detailed benchmarks, so I cannot say how exactly the performance it.
Of course some problems might exist. Welcome to try it and report the problems/bugs to me.