Good morning is the correct one.
Good morning is used to say hello politely when people first see each other in the morning; sometimes also used formally when people leave each other in the morning.
In an informal way, you can just say Morning.
![Good Morning or Good morning?](https://copy-paste-emails.com/wp-content/uploads/2020/05/just-copy-paste.jpg)
Good morning is the correct one.
Good morning is used to say hello politely when people first see each other in the morning; sometimes also used formally when people leave each other in the morning.
In an informal way, you can just say Morning.