C++ login system in the console

loginSystem.cpp

#include <iostream>
#include <fstream>
using namespace std;

int getChoice() {
  cout << endl << "LOGIN SYSTEM" << endl;
  cout << "(1) Create account" << endl;
  cout << "(2) Login" << endl;
  cout << "(3) Quit application" << endl;
  int choice;
  cin >> choice;
  return choice;
}

string getEmail() {
  string email;
  cout << "Email: ";
  cin >> email;
  return email;
}

string getPassword() {
  string password;
  cout << "Password: ";
  cin >> password;
  return password;
}

bool auth(string email, string password) {
  string line;
  bool foundEmail;
  fstream fs;
  fs.open("data.txt", fstream::in);
  while (getline(fs, line)) {
    if (line == email) {
      foundEmail = true;
    }
    if (line == password && foundEmail) {
      fs.close();
      return true;
    }
  }
  return false;
}

void createAccount(string email, string password) {
  fstream fs;
  fs.open("data.txt", fstream::app);
  fs << endl << email << endl << password;
  fs.close();
}

int main() {
  bool running = true;
  string email, password;
  int choice;
  while (running) {
    choice = getChoice();

    switch (choice) {
      case 1:
        email = getEmail();
        password = getPassword();
        createAccount(email, password);
        cout << endl << "ACCOUNT CREATED" << endl;
        break;

      case 2:
        email = getEmail();
        password = getPassword();
        if (auth(email, password) == true) {
          cout << endl << "LOGGED IN" << endl;
          break;
        }
        else {
          cout << endl << "INVALID CREDENTIALS" << endl;
          break;
        }

      case 3:
        running = false;
        break;
    }
  }
  return 0;
}