the first character does in fact mean “good” (here used in the sense of the exclamation OK) and the other two form the phrase used to express “come in” (like answering a door knock)
好(了), 进去 means Ok/alright, go in / get in. 进去 marks motion inward with 去, typically away from the speaker’s deictic center. 进来 would instead mark motion inward toward the speaker’s location or perspective, so would sound more like inviting someone to come in.
the first character does in fact mean “good” (here used in the sense of the exclamation OK) and the other two form the phrase used to express “come in” (like answering a door knock)
Not really for that. You would use 进来, 请进, or just 来/来来 in casual speech. The 来 derivative handles the invitation.
进去 marks movement into a space away from the speaker. It is for actual entry, not invitation. Eg:
胡同太窄, 救护车开不进去
(Hútòng tài zhǎi, jiùhùchē kāi bù jìnqu.)
The lane is too narrow for the ambulance to drive in.
Damn, what should it have been for [climb inside]?
You had it right
好(了), 进去 means Ok/alright, go in / get in. 进去 marks motion inward with 去, typically away from the speaker’s deictic center. 进来 would instead mark motion inward toward the speaker’s location or perspective, so would sound more like inviting someone to come in.