Why can't I read the value outside an observable

I am new to swift and trying to teach myself how to build and iOS app. I hooked up the backend to a Firebase Realtime Database and I am able to successfully read and write to the DB but I cannot access the values outside of an observable.

import UIKit
import Firebase

class ViewController: UIViewController {
    
    var ref:DatabaseReference!
    var test12:String!
    
    override func viewDidLoad() {
        
        self.ref = Database.database().reference()
        
        self.ref.child("Title").child("Name").observe(.value) { snapshot in
            self.test12 = snapshot.value! as? String
            print(self.test12!)
        }
        print(self.test12!)
        super.viewDidLoad()
    }
}

The first print(self.test12!) prints out correctly so I know I am getting the correct information from there DB, but the second one errors out. How can I use the information I get back from the DB throughout my program?