hopefully that's all you will ever see.
My boy would do the same thing at the door and I never discouraged it. I have a mud room at my entrance, so basically surrounded by walls on all sides except the doorway. One day, when he was about a year, a neighbor walked inside while I was in the shower. Gargamel lunged at him. I was really nervous he would attack people and I might lose my boy or have to put him down. I had his temperament tested, he passed with flying colors. The problem was he was cornered in my entrance way and probably got scared and when dogs get scared they can lunge or bite. It might not be aggression in your second instance. I would make sure to not let him approach doors by himself. As soon as I hear someone coming or is I am expecting anyone, I put him in a sit/stay on his bed, let the people enter my house (even if he knows them) until they are fully in the house I then tell Mel its OK to go say hi.
teaching him to go to his bed (or a designated spot away from the doorways) was a life saver for me. I have not had another issue with people arriving since. and I now lock my door when I am in the shower, lol.