website/web/templates/errors/error.html

{{define "content"}}
<div class="container">
    <section class="hero block is-danger is-bold">
        <div class="hero-body">
            <div class="container">
                <h1 class="title">{{.Header}}</h1>
            </div>
        </div>
    </section>

    <div class="block">
        {{.Message}}
    </div>
</div>
{{end}}