I have dozens of "unused" warning in my src/lib, which is surprising, as I specifically indicated this my "library" module. I have searched on internet to see if I have somehow incorrect project structure, but it doesn't seem like it:
I guess these warnings are on code which is not only not used by the library itself, but also not exported, i.e. can't be used when this library is added as a dependency.
By the way, it looks like you have done something strange with your file layout. Normally the root file of a library crate (that Cargo will automatically use) is src/lib.rs, not src/lib/mod.rs. It is unidiomatic to change that default if you don't have to.