Read metatags in a Onebox plugin

Hello,

I had an attempt to create a plugin which increases the unfurled image size within a discourse post for our domain (count.co). This is a link example:
https://count.co/stackoverflow/share/hnT-t1UMfSLTSscX46p9k
This is my onebox plugin attempt:
This is my onebox plugin attempt
Although the plugin does unfurl the image fine, I am struggling to get the og metatags from the website displayed.

register_css <<CSS
.reference {
  position: relative;
  height: 100%;
  width: 100%;
}
.count-embed {
  position: relative;
  height: 400px;
  border: 1px solid #ddd;
  border-radius: 3px;
}

.count-container {
  position: absolute;
  top: 33px;
  bottom: 1px;
  left: 1px;
  right: 1px;
}
CSS

Onebox = Onebox
class Onebox::Engine::CountOnebox
  include Onebox::Engine
  # include Onebox::Engine::StandardEmbed
  def self.priority
    0
  end

  REGEX = /^https:\/\/count.co\/(\w+)\/share\/(.+)/
  matches_regexp REGEX
  def id
    @url.match(REGEX)[2]
  end
  def url
    return @url
  end
  def get_opengraph
    @opengraph ||= ::Onebox::OpenGraph.new(html_doc)
  end
  def html_doc
    return @html_doc if @html_doc

    headers = nil
    headers = { 'Cookie' => options[:cookie] } if options[:cookie]

    @html_doc = Onebox::Helpers.fetch_html_doc(url, headers)
  end
  def og
    @og = get_opengraph
  end
  def to_html 
      <<HTML
      <div class= "count-embed">
      <p> "Explore this data with Count"</p>
      <h3><a href='#{og[:url]}' target="_blank">'#{og[:title]}'</a></h3>
      <div class= "count-container">
      <img src="https://storage.googleapis.com/count-data/shared-visuals/#{id}.png" width="500" height="300" frameborder="0" >
      <p>'#{og[:description]}'</p>
      </div>
    </div>
HTML
  end
end

Thanks in advance

Nicolas