title: How to fetch initial values for session in svelte/sapper
body: <p>I am using svelte/sapper with polka. I have some initial values to be fetched and stored in session from a web service before any page is loaded. What is the best recommended way to do this. </p>
  
  <p>I tried doing this in _layout in the root. But as the fetch is asynchronous, values are not available in the first page load. </p>