Flask Gevent upload ValueError: I/O operation on closed file.

from flask import Flask
from flask import copy_current_request_context
from flask import request
from flask import render_template
import gevent
from flask_socketio import SocketIO

app = Flask(__name__, static_url_path='/static', static_folder='./static')
app.secret_key = "asdf"  # constants.SECRET_KEY
socketio = SocketIO(app)


@app.route("/",methods=["POST","GET"])
def home():
    with app.app_context():
        @copy_current_request_context
        def upload_files():
            def upload_file(fileobj):
                print(fileobj.read())
            print("Started")
            selected_files = request.files.getlist('files[]')
            print(selected_files)
            for selected_file in selected_files:
                print("filename:", selected_file.filename)
                gevent.spawn(upload_file, selected_file)
            print("Finished")

        if request.method == "POST":
            upload_files()
            # gevent.spawn(upload_files)  # raise ClientDisconnected()
            # werkzeug.exceptions.ClientDisconnected: 400 Bad Request: The browser (or proxy) sent a request that this server could not understand.
    return render_template('index.html')

if __name__ == "__main__":
    socketio.run(app, debug=True)