Added check for '/' in username and warns user

helpers/authenticationHelpers.go

@@ -24,6 +24,10 @@ func RegisterUser(db *gorm.DB, username string, password string, password2 strin
 		return model.User{}, errors.New("You have to enter a valid email address")
 	}
 
+	if CheckInvalidUsername(username) {
+		return model.User{}, errors.New("Username contains an invalid character, '/'")
+	}
+
 	if CheckUsernameExists(db, username) {
 		return model.User{}, errors.New("The username is already taken")
 	}
@@ -48,6 +52,10 @@ func CheckUsernameExists(db *gorm.DB, username string) bool {
 	return err == nil
 }
 
+func CheckInvalidUsername(username string) bool {
+	return strings.Contains(username, "/")
+}
+
 func CheckUserEmail(email string) bool {
 	return strings.Contains(email, "@")
 }