drupal_set_title not working in module form - drupal

Question

I´m trying to learn Drupal 8. So now, I´m "building" forms.
I created a module.
INSIDE mymodule\src\Form
I have form1.php
namespace Drupal\mymodule\Form;
use Drupal\Core\Form\FormBase;
use Drupal\Core\Form\FormStateInterface;
class form1 extends FormBase {
public function getFormId() {
return 'myform1';
}
public function buildForm(array $form, FormStateInterface $form_state) {
$form['name'] = array(
'#type' => 'textfield',
'#title' => t('Your name'),
'#maxlength' => 30,
);
$form['Lastname'] = array(
'#type' => 'textfield',
'#title' => t('Your lastname'),
);
$form['submit'] = array(
'#type' => 'submit',
'#value' => t('Submit'),
);
return $form;
}
And WORKS...
But when I want to put a title to the page, in my case and linked to my_module.routing.yml, 127.0.0.1/form1 using
...
public function buildForm(array $form, FormStateInterface $form_state) {
drupal_set_title(t('This is a Title'));
$form['name'] = array(
'#type' => 'textfield',
'#title' => t('Your name'),
'#maxlength' => 30,
);
...
I receive the following ERROR:
ERROR:
Fatal error: Call to undefined function Drupal\mymodule\Form\drupal_set_title() in C:\xampp\htdocs\drupalwebsite\modules\custom\mymodule\src\Form\form1.php on line 16
An the line 16 is:
drupal_set_title(t('This is a Title'));
So the problem is with the title. I tried to resolve it but I could not.
Anyone know why?
Thanks a lot

Answer 1

According to https://www.drupal.org/node/2067859, drupal_set_title() was removed in D8. Have you tried the alternate method that's mentioned in that link, like this:
$form['#title'] = $this->t('This is a Title');