BehaviourSubject: There should be a way to register a handler without firing it immediately.

RxJS version:
Current
Code to reproduce:
(BehaviourSubject)
Expected behavior:
To register a handler without firing the function.
Actual behavior:
Immediately firing handler on subscribe
Additional information:
There should be a way to do so, cause I want to register the handler first then wait for “.next()” to trigger the handler.