fully typed project

app/main.py

@@ -5,7 +5,7 @@ import logger
 import utils
 from server import Server
 
-def _handle_exit(sig, frame):
+def _handle_exit(sig, frame) -> None:
     print("Exiting...")
     sys.exit(0)
 
@@ -17,13 +17,14 @@ def _get_environment_variable(key: str) -> str:
 
     return value
 
-def _parse_environment_variable(key: str, value: str) -> int | None:
+def _parse_environment_variable(key: str, value: str) -> int:
     try:
         return int(value)
     except ValueError:
         logger.error(f"Environment variable '{key}' must be an integer")
+    return -1
 
-def main():
+def main() -> None:
     signal.signal(signal.SIGTERM, _handle_exit)
     signal.signal(signal.SIGINT, _handle_exit)