根据文档:

接下来，只需将方法添加到您的控制器中，并以HTTP动词作为前缀 他们回应

Next, just add methods to your controller, prefixed with the HTTP verb they respond to

所以:

class UserController extends BaseController {

    public function getIndex() 
    {
        // Would response to /user and /user/index
    }
}

因此，在您的情况下，只需将showWelcome()重命名为getWelcome()就足够了.

So, in your case simply renaming showWelcome() to getWelcome() should suffice.