Examine this FastAPI code snippet for background file saving:

Examine this FastAPI code snippet for background file saving:

async def save_file(file: UploadFile):
    content = await file.read()
    with open(file.filename, "wb") as f:
        f.write(content)

@app.post("/upload")
async def upload(file: UploadFile, background_tasks: BackgroundTasks):
    background_tasks.add_task(save_file, file)
    return {"message": "Upload started"}

What is the main issue with this implementation?