How to render context when we open template from S3buckets?

I'm trying to render context in template. But I'm unable to do that. I'm opening my template from bucket and reading. Now how to render context.

    render_param.update({'name': email.split("@")[0],'email': email})
    # html_message = loader.render_to_string(obj.html_template.url, request_data)
    html_message = default_storage.open(obj.html_template.name, 'r')
    html_message= f"""
    {html_message.read()}
    """
    message = EmailMultiAlternatives(subject, html_message, email_host.email, [email])

    message.attach_alternative(html_message, 'text/html')
    messages.append(message)