The (functionally harmless) error is still there in your code, though. Not using 24.0 doesn’t make it go away 
So perhaps it is better to stick with 24.0 and clear out the issues?
There was one of these warnings in Phoenix that I first noticed when upgrading to 24.0, but it was already fixed in a new release. (A Plug.Conn struct was getting updated, but that updated struct was never being used or returned to the caller, so “never used” .. )
