Get post id from shortcode

gtps.php

<?php
add_shortcode( 'table', 'ssl_table_shortcode' );

/**
 * Render ACF table shortcode given several parameters 
 */
function ssl_table_shortcode($atts) {
	global $post;

	// extract the necessary attributes
	extract( shortcode_atts( array(
				'type' => '1',
					), $atts ) );

	// get the html for given table type
	switch ( $type ) {
		case '1':
			$out = ssl_tab_one( $post->id );
			break;
		case '2':
			$out = ssl_tab_two( $post->id );
			break;
		case '3':
			$out = ssl_tab_three( $post->id );
			break;
	}

	return $out;
}