improve db connection functions

src/repository/common.py

@@ -1,6 +1,6 @@
 from typing import Generator
 from sqlalchemy import create_engine
-from sqlalchemy.orm import sessionmaker
+from sqlalchemy.orm import sessionmaker, Session
 from contextlib import contextmanager
 
 from dotenv import load_dotenv
@@ -8,15 +8,19 @@ import os
 
 load_dotenv()
 
-DATABASE_URL = os.getenv("DATABASE_URL")
-engine = create_engine(DATABASE_URL)
-SessionLocal = sessionmaker(bind=engine)
+def get_engine():
+    database_url = os.getenv("DATABASE_URL")
+    if not database_url:
+        raise ValueError("DATABASE_URL is not set in environment variables")
+    return create_engine(database_url)
 
 @contextmanager
-def get_session() -> Generator:
+def get_session() -> Generator[Session, None, None]:
     """
     Get a connection to the Postgres database
     """
+    engine = get_engine()
+    SessionLocal = sessionmaker(bind=engine)
     db = SessionLocal()
     try:
         yield db