Code Snippet 2 - https://solusipress.com/sisi-koding-wordpress-custom-post-dan-custom-fields/

snippet-2.php

<?php
add_action( 'cmb2_admin_init', 'solusipress_event_detail_metaboxes' );
add_action( 'cmb2_admin_init', 'solusipress_event_price_metaboxes' );

function solusipress_event_detail_metaboxes() {
	
  	$prefix = '_spevt_';	  
  
	$cmb = new_cmb2_box( array(
		'id'            => 'spevt_event_metabox',
		'title'         => __( 'Event Detail', 'cmb2' ),
		'object_types'  => array( 'event', ), // Post type
		'context'       => 'normal',
		'priority'      => 'high',
		'show_names'    => true,
	) );  

	$cmb->add_field( array(
		'name'       => __( 'Start Date/Time', 'cmb2' ),
		'id'         => $prefix . 'start_date',
		'type'       => 'text_datetime_timestamp',
	) );  
  
	$cmb->add_field( array(
		'name'       => __( 'End Date/Time', 'cmb2' ),
		'id'         => $prefix . 'end_date',
		'type'       => 'text_datetime_timestamp',
	) );  
  
	$group_field_id = $cmb->add_field( array(
		'id'          => $prefix.'sponsor_group',
		'type'        => 'group',
		'description' => __( 'Sponsors', 'cmb2' ),
		'options'     => array(
			'group_title'   => __( 'Sponsor {#}', 'cmb2' ), // since version 1.1.4, {#} gets replaced by row number
			'add_button'    => __( 'Add Sponsor', 'cmb2' ),
			'remove_button' => __( 'Remove Sponsor', 'cmb2' ),
			'sortable'      => true, // beta
			'closed'     => false,
		),
	) );

  	$cmb->add_group_field( $group_field_id, array(
		'name' => 'Company',
		'id'   => 'company',
		'type' => 'text',
	) );

	$cmb->add_group_field( $group_field_id, array(
		'name' => 'Logo',
		'description' => 'Upload image file for company logo',
		'id'   => 'logo',
		'type' => 'file',
	  	'options' => array(
			'url' => false, // Hide the text input for the url
		),
		'text'    => array(
			'add_upload_file_text' => 'Add Image'
		),
	  	'query_args' => array(
			'type' => array(
				'image/jpg',
			  	'image/jpeg',
				'image/png',
			),
		),
		'preview_size' => 'large'
	) );  
  
	$cmb->add_group_field( $group_field_id, array(
		'name' => 'Website',
		'id'   => 'company_url',
		'type' => 'text_url',
	) );
  
}

function solusipress_event_price_metaboxes() {
  
  	$prefix = '_spevt_';	  
  
	$cmb = new_cmb2_box( array(
		'id'            => 'spevt_event_price',
		'title'         => __( 'Event Price', 'cmb2' ),
		'object_types'  => array( 'event', ), // Post type
		'context'       => 'side',
		'priority'      => 'high',
		'show_names'    => true, // Show field names on the left
	) );  
  	
	$cmb->add_field( array(
		'name' => __( 'Ticket Price', 'cmb2' ),
	  	'desc' => __( 'Leave empty for free event', 'cmb2' ),
		'id'   => $prefix.'price',
		'type' => 'text_money',
	  	'before_field' => 'IDR',
	) );
  	
  	$cmb->add_field( array(
		'name' => __( 'Buy URL', 'cmb2' ),
	  	'desc' => __( 'Link to buy the ticket (e.g. https://tiket.com/awesome-event-by-solusipress)', 'cmb2' ),
	  	'id' => $prefix.'buy_url',
	  	'type' => 'text_url',
	) );
  	
}