Planted first seed

i planted my first seed today, i germinated it in advance and started the 18/6 cycle at 12 noon today...i have one little problem, i understand that for the 6 hours of no light it needs to be complete darkness...i am planning to do this grow in my closet and the closet door needs to be fixed so it will close completely, would it be suitable to just put a black garbage bag (with ventilation holes of course) over the plant during the 6 hours without light? or will that not achieve the same effect for whatever reason?

In veg it does not need complete darkness, in fact you can just leave the lights on 24 hrs.
Complete darkness needs to be accomplished by the time you want to flower (12/12). A simple way to do this is some black plastic on the inside of the door, if the door opens out, just hang it and roll up when you need access, if the door opens in, then attach a larger than door size piece of plastic to the door to cover all the gaps.

You don't want to bag the plants, they won't like it.

thanks man

Anything you need feel free to ask!!!
Good luck and happy growing!