Asynchronous Python with eel

Question

I am creating a desktop app with the use of eel. However, I am having an issue with running functions at the same time.

The idea of eel is that it allows electron to communicate with Python via JS. So, I have created a button in the eel UI that runs part of my program (multiple asynchronous aiohttp sessions). The function that runs those is defined as asynchronous, i.e. async def main():. And all of the functions run by main() are also async. Here is a general outline of the program:

import eel
import asyncio
from aiohttp import ClientSession

options = {
    'mode': 'custom',
    'args': ['node_modules/electron/dist/electron.exe', '.'],
}


@eel.expose
async def start_program():  # this is run when the user clicks the run button
    await main()


@eel.expose
async def test_print():  # this is run when the user clicks the test button
    print("test")


async def main():
    tasks = []
    loop = asyncio.get_event_loop()
    for i in range(instances):
        task = asyncio.ensure_future(launch(url))
        tasks.append(task)
    loop.run_until_complete(asyncio.wait(tasks))


async def launch(url):
    done = False
    async with ClientSession() as session:
        while not done:
            async with session.get(url, timeout=40) as initial:
                html_text = await initial.text()
                if x in html_text:
                    done = True
        await session.close()



if __name__ == "__main__":
    eel.init('web')
    eel.start('html/index.html', options=options)

And then in my JavaScript I have:

async function start_program_js() { // this is run when the user clicks the run button
    await eel.start_program()();
}

async function test_print_js() { // this is run when the user clicks the test button
    await eel.test_print()();
}

So, the desired output is that once I have already pressed the "run" button, if I then click the "test" button, it will print "test". However, at the moment, neither are running. I could get "run" to work by changing async def main(): to def main():, async def start_program(): to def start_program(): and async def test_print(): to def test_print():. Then in the JS I changed it to

function start_program_js() { // this is run when the user clicks the run button
    eel.start_program();
}

function test_print_js() { // this is run when the user clicks the test button
    eel.test_print();
}

However, now my issue is that the "test" button will not do anything if I have already clicked "run". It works by itself, but not if "run" is running.

I thought the async approach I detailed first would work, but using that and clicking "run" caused this error:

Traceback (most recent call last):
  File "src\gevent\greenlet.py", line 766, in gevent._greenlet.Greenlet.run
  File "C:\Users\x\AppData\Local\Programs\Python\Python37-32\lib\site-packages\eel\__init__.py", line 209, in _process_message
    'value': return_val    }))
  File "C:\Users\x\AppData\Local\Programs\Python\Python37-32\lib\json\__init__.py", line 231, in dumps
    return _default_encoder.encode(obj)
  File "C:\Users\x\AppData\Local\Programs\Python\Python37-32\lib\json\encoder.py", line 199, in encode
    chunks = self.iterencode(o, _one_shot=True)
  File "C:\Users\x\AppData\Local\Programs\Python\Python37-32\lib\json\encoder.py", line 257, in iterencode
    return _iterencode(o, 0)
  File "C:\Users\x\AppData\Local\Programs\Python\Python37-32\lib\json\encoder.py", line 179, in default
    raise TypeError(f'Object of type {o.__class__.__name__} '
TypeError: Object of type coroutine is not JSON serializable
2019-06-03T13:00:59Z <Greenlet at 0x4f4b4b0: _process_message({'call': 6.074835210306471, 'name': 'start_program', 'ar, <geventwebsocket.websocket.WebSocket object at 0x0)> failed with TypeError

C:\Users\x\AppData\Local\Programs\Python\Python37-32\lib\site-packages\gevent\libuv\loop.py:193: RuntimeWarning: coroutine 'start_program' was never awaited
  super(loop, self)._run_callbacks()
RuntimeWarning: Enable tracemalloc to get the object allocation traceback

Does anyone know how I can resolve this issue?

Thanks.

EDIT: I just noticed there is an asynchronous section in the readme. I have tried to replicate it, but I can't get it working. I tried

@eel.expose
def start_program():  # this is run when the user clicks the run button
    eel.spawn(main)


@eel.expose
def test_print():  # this is run when the user clicks the test button
    eel.spawn(test_print_x)


def test_print_x():
    print("test")

However, I'm having the same issue as before, i.e. it is not running the "test" button function.