Use Application.app_dir/2 instead of :code.priv_dir

lib/music_library/records/cover.ex

@@ -1,8 +1,7 @@
 defmodule MusicLibrary.Records.Cover do
   @size 600
 
-  @fallback_path :code.priv_dir(:music_library)
+  @fallback_path Application.app_dir(:music_library, ["priv", "cover-not-found.jpg"])
-                 |> Path.join("/cover-not-found.jpg")
 
   @external_resource @fallback_path
 

lib/music_library/repo.ex

@@ -25,8 +25,8 @@ defmodule MusicLibrary.Repo do
         :linux -> "so"
       end
 
-    Path.join([
+    Application.app_dir(:music_library, [
-      :code.priv_dir(:music_library),
+      "priv",
       "sqlite_extensions",
       platform,
       "#{name}.#{extension}"