Add: backend session support and bug fix

pkg/database/method_user.go

@@ -22,10 +22,21 @@ func (database *Database) LoginAsAnonymous() (*User, error) {
 	return user, nil
 }
 
-func (database *Database) Register(username string, password string, usertype int64) (error) {
+func (database *Database) Register(username string, password string, usertype int64) (*User, error) {
 	_, err := database.stmt.insertUser.Exec(username, password, usertype, 0)
 	if err != nil {
-		return err
+		return nil, err
 	}
-	return nil
+	return database.Login(username, password)
+}
+
+func (database *Database) GetUserById(id int64) (*User, error) {
+	user := &User{}
+
+	// get user from database
+	err := database.stmt.getUserById.QueryRow(id).Scan(&user.ID, &user.Username, &user.Role, &user.AvatarId)
+	if err != nil {
+		return user, err
+	}
+	return user, nil
 }