Hello,
You can install it with luarocks:
I am aware of the other project,
https://github.com/azurewang/lua-resty-postgres There is some missing functionality in it and I originally started writing my own to learn more about the protocol to contribute but it turned out simple enough and I just implemented everything I needed. I also had the additional requirement for running the library outside of openresty which I've also implemented.
The project is fully tested and I'm running it on all of my projects now in production and it works great.
Thanks for checking it out