Transitioning from co sleeping

We have coslept since our little boy was born September 2016. We are expecting another baby August of this year. We want to transition our little boy to his own room. The past few nights I have laid with him in his room(in a full bed) until he falls asleep and then I get up and go to my bed. He will sleep in there until 1 or 2am and then he wakes up and stands in the hallway until I go get him. Any tips on how to keep him in his bed all night? He has slept through the night until this😑