`prompt_async` is blocking on windows

Consider the following:

import asyncio

from prompt_toolkit.shortcuts import prompt_async

async def spam():
    while True:
        print("hello");
        await asyncio.sleep(0.1);
        print("World");
        await asyncio.sleep(0.1);


async def my_coroutine():
    while True:
        result = await prompt_async('Say something: ', patch_stdout=True)
        print('You said: %s' % result)

loop = asyncio.get_event_loop()
loop.run_until_complete(asyncio.gather(my_coroutine(), spam()))
loop.close()

What I expect to happen: The prompt is pushed down by a continual stream of Hello and World

What actually happens: Each time I push a single character, an extra Hello or World is printed - the output does not advance while waiting for a single character.

Reproduce the provided prompt_async and asyncio.gather example on Windows, starting at the prompt_async entry point and its interaction with the event loop. Confirm that spam continues printing while the prompt waits for input, and verify the behavior with the example after the issue is addressed.