How to make firebase asynchronous function run in order

Question

I have these two functions. What this does is check if the my firebase realtime database has a users UUID in it or not. Unfortunately I found this code does not work. I thought this would run in order but my function isIDUsed() gets returned before the database has a chance to check if the value exists or not. So it always returns the value inDatabase is initialized in. Which is false

I have tried to implement a semaphore but im new to swift and just cant seem to get the syntax correct. Please let me know if you have a solution thank you

func isIdUsed(ID: String) -> Bool{
    var databasedictionary: NSDictionary = NSDictionary()
    var inDatabase = false
    
    
    devindatabse.child("TotalUsers").observeSingleEvent(of: .value, with: { snapshot in
        let value = snapshot.value as? NSDictionary

        databasedictionary = value! as NSDictionary

        if totalUsersCheck(totalUsers: databasedictionary, ID: ID) {
            inDatabase = true
                
        }
          // ...
    }) { error in
        print(error.localizedDescription)
    }
    
    return inDatabase

}


func totalUsersCheck(totalUsers: NSDictionary, ID: String) -> Bool{
 
    if totalUsers[ID] != nil {
        return true
    }
    return false
}