What happens when a message is published with QoS=1?

[ZeeD]

I would like to have a better understanding of the behavior of this library.
Specifically: let's say I have an open connection (over WSS, if this change anything) with an MQTT server.
I publish a message with QoS=1.
My understanding is that mqtt awaits for a PUBACK message. After the ack has been received, the done callback is called and the flow is ended.
What is not clear to me is the low-level stuff: how much "time" do the library awaits for the ack? what happen if the ack doesn't come? the message is resent? the connection is closed/reopened? something else?
Is this behavior tunable?