Getting "java.lang.NullPointerException" error which trying to call the a function to take screenshot in a test method on Selenium

Question

I am new to the selenium automation world, Getting java.lang.NullPointerException error which trying to call the function to take a screenshot in a test method on Selenium. I am pretty sure I have missed initialize or return the driver somewhere. below is the code.

baseTest class where I am initializing the webdriver

public class baseTest {
    public Properties objProp = new Properties();
    FileInputStream readProp;
        {
        try {
            readProp = new FileInputStream("C:\\Users\\kiran\\IdeaProjects\\SelProject2\\src\\test\\java\\appDetails.properties");
            objProp.load(readProp);
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    protected WebDriver driver;

    @BeforeClass
    public void beforeSuite()
    {
        System.setProperty(objProp.getProperty("browser"),objProp.getProperty("driverPath"));
        driver = new ChromeDriver();
        driver.manage().window().maximize();
        driver.manage().timeouts().implicitlyWait(30, TimeUnit.SECONDS);
        driver.get(objProp.getProperty("URL"));
    }

    @AfterSuite
    public void afterSuite()
    {
        if(null != driver)
        {
            driver.close();
            driver.quit();
        }
    }

    public WebDriver getDriver()
    {
        return driver;
    }
}

All my tests extends the baseTest function link shown below

public class loginFunction extends baseTest {

    guruLoginPage objLogin;
    guruHomePage objHome;
    takeScreenshot objSS = new takeScreenshot(driver);
    //readExcel readObj;


    @Test
    public void performLogin() throws IOException, InterruptedException {
        objLogin = new guruLoginPage(driver);
        String loginPageTitle = objLogin.getTitle();
        Assert.assertTrue(loginPageTitle.contains("Demo Site"));

        objSS.screenshot();

        objLogin.loginAction(objProp.getProperty("appUsername"), objProp.getProperty("appPassword"));
        Thread.sleep(2000);

        objHome = new guruHomePage(driver);

        Assert.assertTrue(objHome.validateLogin().contains("Manger Id : mngr242657"));
        Thread.sleep(2000);
        objSS.screenshot();
    }
}

when i write this piece of code in the loginfunction, it works fine, but when i am trying to optimize and put it in a separate class and call the method I am getting java.lang.NullPointerException error

public class takeScreenshot{

    WebDriver driver;


    public takeScreenshot(WebDriver driver)
    {
            this.driver=driver;
            PageFactory.initElements(driver,this);
    }

    public void screenshot() throws IOException {
        String fileSuffix = DateTime.now().toString("yyyy-dd-MM-HH-mm-ss");
        TakesScreenshot ss = ((TakesScreenshot)this.driver);
        File srcFile = ss.getScreenshotAs(OutputType.FILE);
        FileUtils.copyFile(srcFile,new File("C:\\Users\\kiran\\IdeaProjects\\SelProject2\\src\\test\\java\\Screenshots\\"+fileSuffix+".jpg"));
    }
}