async resolvers in graphene breaks using nested structures

[raix]

Using python 3.6, linux+mac

I'm trying to fetch data via http but the nested call hangs - this can be replicated by using asyncio.sleep

Replication: comment out asyncio.sleep in fakeFetch to see the difference

from flask import Flask
from flask_graphql import GraphQLView
from graphql.execution.executors.asyncio import AsyncioExecutor
import graphene
import asyncio
import sys

app = Flask(__name__)

def Log(message):
    print(f"LOG: {message}", file=sys.stderr)

async def fakeFetch():
    Log('Wait a sec...')
    await asyncio.sleep(1) # Comment this out and things work
    return 'Async World'

class Bars(graphene.ObjectType):
    bar = graphene.String()
    async def resolve_bar(self, args, context, info):
        await fakeFetch()
        return 'Bar'

class Foo(graphene.ObjectType):
    bars = graphene.Field(Bars)
    async def resolve_bars(self, args, context, info):
        await fakeFetch()
        return Bars()

class Query(graphene.ObjectType):
    foo = graphene.Field(Foo)

    def resolve_foo(self, args, context, info):
        return Foo()

schema = graphene.Schema(query=Query)

app.add_url_rule('/graphql', view_func=GraphQLView.as_view('graphql', schema=schema, graphiql=True, executor=AsyncioExecutor() ))

if __name__ == "__main__":
    app.run()

Query:

{
  foo {
    bars {
      bar
    }
  }
}

requirements.txt

async-timeout==1.1.0
chardet==2.3.0
click==6.7
Flask==0.12
Flask-GraphQL==1.4.0
graphene==1.1.3
graphql-core==1.0.1
graphql-relay==0.4.5
itsdangerous==0.24
Jinja2==2.9.4
MarkupSafe==0.23
multidict==2.1.4
promise==1.0.1
six==1.10.0
typing==3.5.3.0
Werkzeug==0.11.15
yarl==0.8.1