How to query WordPress posts with a custom taxonomy term.

wp-query-custom-taxonomy.php

<?php
$posts = get_posts(
    array(
        'numberposts' => 20,
        'post_type' => 'custom_post_type',
        'tax_query' => array(
            array(
                'taxonomy' => 'custom_taxonomy',
                'field'    => 'slug',
                'terms'    => array( 'termslug1', 'termslug2' )
            )
        )
    )
);