if cat is 2 show specific sidebar wordpress

I am trying to get a specific sidebar show when post is in specific categories but the code that I have doesn’t seems to work.

Here is the code:

<div class="sidebar">
<?php if (is_single() && in_category('2') ) { ?>
<?php dynamic_sidebar( 'blog-sidebar' ); ?>
<?php } else { ?>
<?php dynamic_sidebar( 'general-sidebar' ); ?>
<?php }
    <!-- Load posts related to current post -->
$currentcat = get_query_var('cat');
    $relatedargs = array (
    'cat'                       =>  'array($currentcat)',
    'posts_per_page'            =>  '2',
    'ignore_sticky_posts'       =>  true,
    'orderby'                   =>  'rand',
    'post__not_in'                      =>  array( $post->ID ),
    'cat'                                           =>  '-1'
); 
    $relatedposts = new WP_Query( $relatedargs ); ?>
<?php if ( $relatedposts->have_posts() ) : ?>
<?php  while ($relatedposts -> have_posts()) : $relatedposts -> the_post(); ?>
<div <?php post_class('col-4')?>>
    <h3><a class="h3" href="<?php the_permalink(); ?>"><?php the_title(); ?></a></h3>
    <?php 
        global $more;    // Declare global $more (before the loop).
        $more = 0;       // Set (inside the loop) to display content above the more tag.
        the_content("Lees verder ");
    ?>
</div>
<?php endwhile; wp_reset_postdata();?>
<?php endif; ?>
</div><!--/.sidebar -->

But even when I am on post that has cat 2 it still shows the else sidebar. What am I doing wrong?