Update post.html

Author: Daniele-rolli

_layouts/post.html

@@ -34,7 +34,7 @@
     <meta property="og:title" content="{{ page.title }}" />
     <meta property="og:description" content="{{ page.excerpt | strip_html }}" />
     <meta property="og:image" content="{{ site.baseurl }}/{{ page.image }}" />
-    <meta property="og:url" content="{{ site.url }}{{ page.url }}" />
+    <meta property="og:url" content="{{ site.url }}/{{ page.url }}" />
     <meta property="og:site_name" content="{{ site.title }}" />
 
     <!-- Twitter Card Meta Tags -->