Unable to load chrome/gecko driver after using Cucumber Driver Factory - nullpointerexception

Question

This is my first question ever asked here, so I hope I ask it the right way:
I'm working on a multimodule maven project to test a software that is still in a development. I've been using Cucumber, Selenium, JUnit for some time and doing online courses to improve my skills. In one of the tutorials was explained how to use Driver Factory and configuration files so I applied it to my project, but after that was unable to run any of the drivers (gecko/chrome/ie). Here is a big part of the code, so I hope someone can help :)
I catch the exception from the DriverFactory.class:
"Unable to load browser: null"
config.properties file has only one line:
browser=chrome
public class DriverFactory {
public static WebDriver driver;
public WebDriver getDriver() {
try {
//Read Config
ReadConfigFile file = new ReadConfigFile();
String browserName = file.getBrowser();
switch (browserName) {
case "firefox":
if (driver == null) {
System.setProperty("webdriver.gecko.driver", Constant.GECKO_DRIVER_DIRECTORY);
FirefoxOptions options = new FirefoxOptions();
options.setCapability("marionette", false);
driver = new FirefoxDriver(options);
driver.manage().window().maximize();
}
break;
case "chrome":
if (driver == null) {
System.setProperty("webdriver.chrome.driver", Constant.CHROME_DRIVER_DIRECTORY);
driver = new ChromeDriver();
driver.manage().window().maximize();
}
break;
/*case "ie":
if (driver == null) {
DesiredCapabilities capabilities = DesiredCapabilities.internetExplorer();
System.setProperty("webdriver.ie.driver", Constant.IE_DRIVER_DIRECTORY);
capabilities.setCapability("ignoreZoomSetting", true);
driver = new InternetExplorerDriver(capabilities);
driver.manage().window().maximize();
}
*/
}
} catch (Exception e) {
System.out.println("Unable to load browser: " + e.getMessage());
} finally {
driver.manage().timeouts().pageLoadTimeout(60, TimeUnit.SECONDS);
}
return driver;
}
public class ReadConfigFile {
protected InputStream input = null;
protected Properties prop = null;
public ReadConfigFile() {
try {
input = ReadConfigFile.class.getClassLoader().getResourceAsStream(Constant.CONFIG_PROPERTIES_DIRECTORY);
prop = new Properties();
prop.load(input);
} catch(IOException e) {
e.printStackTrace();
}
}
public String getBrowser() {
if(prop.getProperty("browser") == null) {
return "";
}
return prop.getProperty("browser");
}
public class Constant {
public final static String CONFIG_PROPERTIES_DIRECTORY = "properties\\config.properties";
public final static String GECKO_DRIVER_DIRECTORY = System.getProperty("user.dir") + "\\src\\test\\resources\\geckodriver.exe";
public final static String CHROME_DRIVER_DIRECTORY = System.getProperty("user.dir") + "\\src\\test\\resources\\chromedriver.exe";
public class CreateCaseSteps extends DriverFactory {
//Background Steps
#Given("^user accesses the login page$")
public void userAccessesTheLoginPage() throws Throwable {
getDriver().get("http://localhost:8080/");
}
#When("^user enters a valid username")
public void userEntersAValidUsername(DataTable table) throws Throwable {
Thread.sleep(3000);
List<List<String>> data = table.raw();
getDriver().findElement(By.xpath("//input[#placeholder='username']")).sendKeys(data.get(0).get(0));
}
#When("^user enters a valid password")
public void userEntersAValidPassword(DataTable table) throws Throwable {
Thread.sleep(3000);
List<List<String>> data = table.raw();
getDriver().findElement(By.xpath("//input[#placeholder='password']")).sendKeys(data.get(0).get(0));
}
#And("^user clicks on the login button$")
public void userClicksOnTheLoginButton() throws Throwable {
getDriver().findElement(By.xpath("//input[#value='Login']")).click();
}
#Then("^user should be taken successfully to the login page$")
public void userShouldBeTakenSuccessfullyToTheLoginPage() throws Throwable {
Thread.sleep(3000);
WebElement logoutMenu = getDriver().findElement(By.xpath("//i[#class='glyphicon glyphicon-user']"));
Assert.assertEquals(true, logoutMenu.isDisplayed());
}