wordpress plugin - first author shown twice

Question

I'm trying to set up a wordpress plugin in order to show articles authors in wordpress

function inl_users() {
if ( function_exists( 'get_coauthors' ) ) {
  $coauthors = get_coauthors();
  //array_shift($coauthors);
  foreach ( $coauthors as $coauthor ) {
    $autArray[] = '<a href=' . get_author_posts_url( $coauthor->ID ) . '>' . $coauthor->display_name . '</a>';
    echo implode(", ", $autArray);
  }
}

The first author is shown twice in the first element, like this:
for $autArray = (John Smith, Joe Blogs); it returns John SmithJohn Smith, Joe Blogs

html is like this:
<a href="https://example.com/author/john-smith/">John Smith</a><a href="https://example.com/author/john-smith/">John Smith</a>, <a href="https://example.com/author/joe-blogs/">Joe Blogs</a>

as you can see I've tried to use array_shift() because I thought they were two distinct elements, but they are not

any suggestions?

thanks in advance