Hugo-theme-stack/layouts/partials/widget/search.html

<form action="/search" class="search-form widget" {{ with .OutputFormats.Get "json" -}}data-json="{{ .Permalink }}" {{- end }}>
    <p>
        <label>Search</label>
        <input name="keyword" required placeholder="Type something..." />
    
        <button title="Search">
            {{ partial "helper/icon" "search" }}
        </button>
    </p>
</form>