WifiClientSecure blocking ESP8266

I am connecting ESP8266 to AWS IoT Core using this code and it works well and is sending messages.
But I am facing a problem with WifiClientSecure. When it is trying to connect to AWS my code is blocked for like 6 seconds or more depending on the response. But I have some critical proccess happening and my code never can be blocked.

What could I do to make the process asynchronous?

Thanks.
