我想构建一个小型REST API服务器，返回在Binance Exchange WebSocket上监听的最后100笔交易。我使用uvicorn启动应用程序，但返回的json是'{}'。如果我用普通的python命令执行程序，WebSocket的侦听就可以工作，我希望有一个独立的服务器，既响应REST请求，又侦听Binance的websocket。
下面是我的代码：

import websocket
import json
import time
import uvicorn

app = FastAPI()
last_trade = []

def on_message(ws, message):
    global last_trade
    data = json.loads(message)
    if 'e' in data and data['e'] == 'trade':
        last_trades += data
        if len(last_trade) > LASTS:
            last_trade.pop(0)  
             
        # print(data)

def on_error(ws, error):
    print(error)

def on_close(ws):
    print("Connexion fermée")
    reconnect()

def on_open(ws):
    ws.send(json.dumps({
        "method": "SUBSCRIBE",
        "params": ["btctusd@trade"],
        "id": 1
    }))

def reconnect():
    delay = 5  # Délai de reconnexion en secondes
    print(f"Reconnexion dans {delay} secondes...")
    time.sleep(delay)
    connect_to_binance_websocket()

def connect_to_binance_websocket():
    websocket_url = "wss://stream.binance.com:9443/ws"
    ws = websocket.WebSocketApp(websocket_url,
                                on_message=on_message,
                                on_error=on_error,
                                on_close=on_close)
    ws.on_open = on_open
    ws.run_forever()

@app.get("/")
async def root():
    return json.dumps(last_trade)


LASTS=100
if __name__ == '__main__':
    connect_to_binance_websocket()
    uvicorn.run(app, host="0.0.0.0", port=8000)

Thanks

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