searchform.php

<form method="get" id="searchform" action="<?php echo esc_url( home_url() ); ?>/">
    <div class="sidebar-search-form">
        <input type="text" class="search-query form-control" placeholder="<?php esc_html_e('Search', 'offshore'); ?>" name="s" id="s" />
        <button class="btn search-btn" type="button">
            <span class="fa fa-search"></span>
        </button>
    </div>
</form>