WordPress Single Template for a Specific Category

<?php 
function get_custom_cat_template($single_template) { 
  global $post; 
    if ( in_category( 'category-name' )) {
    $single_template = dirname( __FILE__ ) . '/single-template.php';
  } 
  return $single_template;
}

add_filter( "single_template", "get_custom_cat_template" ) ;
?>