redis pubsub: __redisGetSubscribeCallback: Assertion `reply->elements >= 2' failed.

[yegorrr]

is redis pubsub model supported by drogon? it is supported by hiredis, but whenever i issue 'subscribe xxx' command i get this:

vpn: async.c:378: __redisGetSubscribeCallback: Assertion `reply->elements >= 2' failed.

i assume i'd need a separate thread since it's a blocking command, so should i just use hiredis callbacks instead of redisClient->newTransactionAsync ?

[hwc0919]

#1212 Merged