Wei Wang

There is one way to solve this problem:

just build another layer 3 blocks lower than the spawning floor, the iron golem will drop down to this new layer and can be collected by water.
Also, you should add a soild block out of the door to avoid the iron golem spawn inside the door.

Then what happens......Probably without sky light and meanwhile drink potion of night vision?

Weird! Iron Golems can be generated inside a door in the new snapshot........

F3+A couldn't work

My seed is Wisconsin(1900638999), I created my world in 18W16a, and this is my first time to go to mansion (x: 4448, z:-3360)