I am pretty new to use log4rs (even rust to be honest) and don't know the best way to pass the logger to submodule.
I have successfully done the conf. at the main level (and log work) but I don't know how to pass it to module (do I need to pass it as a reference or using lazy_static. Getting confuse at this point and I don't find some proper example.
I haven't used that logging crate, but most logging crates install themselves in a global somewhere and allow you to use info!, warn! and friends as if they were println!.
When you init log4rs, it'll register itself with the log crate as the global logger. You can then use the macros provided by log (info!, warn!, etc. as mentioned by @alice) anywhere in your crate.
log4rs (and most other loggers) use log like this because it allows a shared interface for all binaries and libraries. If any library you use depends on log as well, it can get access to the set global logger without having to be configured manually, or having to depend on any specific logging backend (like log4rs).