=====================================================================
ShareAsset.php <= this is located inside "{module}/assets/" directory
=====================================================================
<?php

namespace core\modules\share\assets;
use yii\web\AssetBundle;

class ShareAsset extends AssetBundle
{
    public $sourcePath = '@core/modules/share/views/share';

    public $css = [
        'css/share.css',
        'css/vendor/stepper.css',
        'css/vendor/bootstrap-select.css'
    ];
    public $js = [
        'js/share.js',
        'js/vendor/stepper.js',
        'js/vendor/bootstrap-select.min.js',
        '@vendor/almasaeed2010/adminlte/bower_components/bootstrap-datepicker/dist/js/bootstrap-datepicker.js'
    ];
    public $depends = [
        'yii\web\YiiAsset',
        'yii\bootstrap\BootstrapAsset',
    ];
    public function init()
    {
        $this->publishOptions['forceCopy'] = true;
    }
}

==========================================================
Share.php <= This is located inside the root of my module
==========================================================
<?php

namespace core\modules\share;

use Yii;
use core\modules\share\assets\ShareAsset;

/**
 * share module definition class
 */
class Share extends \yii\base\Module
{
    /**
     * {@inheritdoc}
     */
    public $controllerNamespace = 'core\modules\share\controllers';

    /**
     * {@inheritdoc}
     */
    public function init()
    {
        parent::init();
        ShareAsset::register(Yii::$app->view);

        // custom initialization code goes here
    }
}