Make pool and poolSong global variables

compose.test.yaml

@@ -10,7 +10,7 @@ services:
     ports:
       - "5433:5432"
     healthcheck:
-      test: ["CMD-SHELL", "pg_isready -U testuser -d music_server_test"]
+      test: ["CMD-SHELL", "pg_isready -U postgres -d postgres"]
       interval: 5s
       timeout: 5s
       retries: 5