refactor: standardize .env loading behavior across modules

- Use .env from current folder for each lightrag instance
- Allow different .env files for different instances
- Make OS env vars take precedence over .env file

lightrag/utils.py

@@ -19,9 +19,10 @@ import tiktoken
 from lightrag.prompt import PROMPTS
 from dotenv import load_dotenv
 
-# Load environment variables
-load_dotenv(override=True)
-
+# use the .env that is inside the current folder
+# allows to use different .env file for each lightrag instance
+# the OS environment variables take precedence over the .env file
+load_dotenv(dotenv_path=".env", override=False)
 
 VERBOSE_DEBUG = os.getenv("VERBOSE", "false").lower() == "true"