[ChangeStream] Why does iterating change stream block and how to avoid it

Hello,

I am trying to use change streams and this code snippet is blocking:

for (const auto& event : stream)

{

    handleEvent(event);

}

I run the above code periodically on different streams. But I see that stream iteration blocks when it is empty and I am not able to break out of this loop if that happens. Why is that the case? How can I read all available events in the stream and not be blocked? I cannot use a break; since I don't know before reading the stream how many events are in there.