使烧瓶返回响应头 http1.1 而不是 http1.0

Question

当我使用flask 1.1.1 时，请求使用http1.1，但响应使用http1.0，

from flask import Flask, request, Response
import json

app = Flask(__name__)


@app.route('/', methods=['GET'])
def index():
    print(request.environ.get('SERVER_PROTOCOL'))
    return Response(json.dumps({'hi': 'hello'}))


if __name__ == '__main__':
    app.run(host='127.0.0.1', port=8080, debug=True)

终端打印是

127.0.0.1 - - [25/Nov/2019 14:42:14] "GET / HTTP/1.1" 200 -
 * Detected change in '/Users/tal/test_redis/flask_ttttt.py', reloading
 * Restarting with stat
 * Debugger is active!
 * Debugger PIN: 840-568-290
HTTP/1.1

它返回

HTTP/1.0 200 OK
Content-Type: text/html; charset=utf-8
Content-Length: 15
Server: Werkzeug/0.15.5 Python/3.7.3

如何将 http 版本 1.0 更改为 1.1？