load dotenv everywhere it's needed; postgresql pool pre ping

app/main.py

@@ -3,6 +3,7 @@ from fastapi import FastAPI, Depends, HTTPException
 from fastapi.middleware.cors import CORSMiddleware
 from strawberry import Schema
 from strawberry.fastapi import GraphQLRouter
+from dotenv import load_dotenv
 
 from auth import router as auth_router, get_user_by_id, get_current_user
 
@@ -22,6 +23,7 @@ Base.metadata.create_all(bind=engine)
 app = FastAPI()
 
 # 获取环境变量字符串，并转成列表
+load_dotenv()
 origins_str = os.getenv("CORS_ORIGINS", "http://localhost:3000")
 origins = [origin.strip() for origin in origins_str.split(",")]