How to Create Custom module in Drupal 8

To create the custom module in Drupal 8 we have to follow the below steps:-
Custom module folder structure custom field for content type

modulename
– modulename/src
— modulename/src/Controller
— modulename/src/Controller/ModulenameController.php
— modulename/src/Plugin
— modulename/src/Plugin/Field
— modulename/src/Plugin/Field/FieldFormatter
— modulename/src/Plugin/Field/FieldFormatter/FieldFormatter.php
— modulename/src/Plugin/Field/FieldType
— modulename/src/Plugin/Field/FieldType/Fieldname.php
— modulename/src/Plugin/Field/FieldWidget
— modulename/src/Plugin/Field/FieldWidget/FieldWidget.php
-modulename/modulename.info.yml
-modulename/modulename.module
-modulename/modulename.routing.yml

-modulename/modulename.info.yml

name: modulename
type: module
description: Description about module.
package: Custom
version: 1.0
core: 8.x

———————————————-
-modulename/modulename.module

/**
 * @File
 * Example custom module for Drupal 8.
 * @author author name
 */ 
/**
 * Implementing hook_menu().
 */

—————————————
-modulename/modulename.routing.yml

 modulename.modulename_page:
  path: '/pagepath'
  defaults:
    _controller: '\Drupal\modulename\Controller\PageController::controller_function_name'
    _title: 'Page Title'
  requirements: 
    _permission: 'access content'