wrap sync call to asyncio.thread

routers/tariffs.py

@@ -1,6 +1,7 @@
 from fastapi import APIRouter
 import aiofiles
 import json
+import asyncio
 from async_lru import alru_cache
 
 router = APIRouter(prefix='/api/v1', tags=['tariffs'])
@@ -9,7 +10,7 @@ router = APIRouter(prefix='/api/v1', tags=['tariffs'])
 async def get_tariffs():
     async with aiofiles.open('data/tariffs.json', 'r', encoding='utf-8') as f:
         content = await f.read()
-    return json.loads(content)
+    return await asyncio.to_thread(json.loads(content))
 
 @router.get('/tariffs')
 async def get_tariffs():