Route [signup] not defined in laravel

Hello stackoverflow community, I am new to laravel. I am learning how to create user registration page. Everything works fine but i am stack in a simple problem.

ErrorException in UrlGenerator.php line 304: Route [signup] not defined. (View: C:\Program Files (x86)\Ampps\www\social\resources\views\welcome.blade.php)

But I defined signup route. Here is my routes.php file

Route::get('/', function () {
  return view('welcome');
})->name('home');
Route::post('/signup', [
    'uses' => 'UserController@postSignUp',
    'as' => 'signup'
]);

And this is my UserController.php

class UserController extends Controller
{
    public function postSignUp(Request $request)
    {
        $email = $request['email'];
        $first_name = $request['frist_name'];
        $password = bcrypt($request['password']);


        $user = new User();
        $user->email = $email;
        $user->frist_name = $first_name;
        $user->password = $password;

        $user->save();

        return redirect()->back();

Blade file is welcome.blade.php

 <form action="" method="post">
         <div class="form-group">
           <label for="email"> Your E-mail </label>
           <input class ="form-control" type="text" id="email" name="email" >
         </div>

I would be much obliged if anyone could help me. Thanks

Oh, Sorry. I forget to mention that I am using Laravel version: 5.4.11

via Chebli Mohamed