tasks_handler locks a Mutex with IndexMap to iterate over all Record values to render them as a part of the Tasks struct:

fn tasks_handler(req: HttpRequest<State>) -> impl Future<Item = HttpResponse, Error = WebError> {
    let tasks: Vec<_> = req
        .state()
        .tasks
        .lock()
        .unwrap()
        .values()
        .cloned()
        .collect();
    let tmpl = Tasks { tasks };
    future::ok(HttpResponse::Ok().body(tmpl.render().unwrap()))
}

If you remember, we added the askama crate to render templates. Create a templates folder in the root of project and add a tasks.html file with some HTML code that contains at least the following rendering table:

<table>
    <thead>
        <tr>
            <th>Task ID</th>
            <th>Timestamp</th>
            <th>Status</th>
        </tr>
    </thead>
    <tbody>
        {% for task in tasks %}
        <tr>
            <td>{{ task.task_id }}</td>
            <td>{{ task.timestamp }}</td>
            <td>{{ task.status }}</td>
        </tr>
        {% endfor %}
    </tbody>
</table>

This is a part of the full template that you can find in the examples folder for this book, but the preceding code contains code for rendering a table with all the tasks extracted from the Tasks struct, which is  implemented as follows:

#[derive(Template)]
#[template(path = "tasks.html")]
struct Tasks {
    tasks: Vec<Record>,
}

Derive the Template type for this struct and attach the template with the template attribute. askama will embed the template into your code. That's very convenient.