title: How to write middleware for grpc (node.js)
body: <p>I'm attaching a metadata to each client grpc service call (containing a token), and <strong>I'd like to validate this token one the server</strong>, once globally (instead of repeating the validation code in each server service definition).</p>
  
  <p>From my understanding, there is something called "<strong>Interceptor</strong>" for <strong>grpc</strong>, which is somewhat similar to http middleware.</p>
  
  <p>Any example for <strong>Nodejs grpc</strong> interceptor? (or any other way to achieve something similar with http middleware?)</p>
  
  <p>Many thanks!</p>