@Chiiruno I ran minimal tests against this to check if the service would boot on an existing install. I have concerns about this:

-        "connection": "user=hydron password=${cfg.password} dbname=hydron sslmode=disable"
+        "connection": "user=hydron password=${cfg.password} host=/run/postgresql dbname=hydron sslmode=disable"

Is the underlying go library smart enough to fallback to password if socket authentication doesn't work all the time? Initial tests say yes, but I'll need someone familiar with the application to do thorough testing.

Also make special note that unless you're running unstable you will likely have to change the host=/run/postgresql to host=/tmp as the location of the socket file has changed since 19.03.

This pull request has been mentioned on Nix community. There might be relevant details there:

https://discourse.nixos.org/t/prs-ready-for-review-may-2019/3032/3

@matthewbauer were you able to test this on existing install?