title: head tags doesn't change in dynamic page with next/head
body: <p>I'm building a Ecommerce site and i'm making the product detail page. I need to change the meta tags of the page according to the product attributes. I'm using the head component from next/head. The problem is that it seems than the metas change only when I inspect the page with chrome dev tools, but when I choose see the source page they don't appear.
  It's important to me that the metas change from server beacuse I need use og metas for facebook sharing.
  I'm using next v9, and i'm using a custom server, also I use _document and _app prebuild pages.</p>
  
  <p>this is my _document page</p>
  
  <p><a href="https://i.stack.imgur.com/NhdsN.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/NhdsN.png" alt="enter image description here"></a></p>
  
  <p>And this is my product detail page</p>
  
  <p><a href="https://i.stack.imgur.com/nKV9z.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/nKV9z.png" alt="enter image description here"></a></p>
  
  <p>and in the chrome view page source option I only see the document head metas but not the product detail page ones.</p>
  
  <p><a href="https://i.stack.imgur.com/Vf89h.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/Vf89h.png" alt="enter image description here"></a></p>
  
  <p>Can anyone help me to unsderstand how I shloud use head? I have tried several examples with no success.</p>
  
  <p>Thanks in advance, and sorry for my english.</p>