How do I call an async function from a callback that is called by a different thread?

Question

The problem I'm facing is that the ROS framework uses normal callbacks while aiohttp+socket.io uses asyncio. I wish to call an async function from within a ROS callback. Example:

#!/usr/bin/env python3

import asyncio
import socketio
import rospy
from aiohttp import web
from rosgraph_msgs.msg import Log

sio = socketio.AsyncServer()
app = web.Application()
sio.attach(app)

def on_rosout(msg):
  sio.emit("message", msg.msg) # THIS DOES NOT WORK

@sio.on('connect', namespace='/')
def connect(sid, environ):
    print("connect", sid)

@sio.on('disconnect', namespace='/')
def disconnect(sid):
    print("disconnect", sid)

app.router.add_static('/', 'html', show_index = True)

if __name__ == "__main__":
    rospy.init_node("foo_node")
    rospy.Subscriber("/rosout_agg", Log, on_rosout)
    web.run_app(app)