add_shortcode('acf_current_user_field', 'acf_current_user_field_shortcode');
function acf_current_user_field_shortcode($atts) {
// extract attributs
extract(shortcode_atts(array(
'field' => '',
'format_value' => true
), $atts));
// get the current user
$user_id = get_current_user_id();
// get value and return it
$value = get_field($field, 'user_'.$user_id, $format_value);
// array
if( is_array($value) ) {
$value = @implode( ', ', $value );
}
// return
return $value;
}