title: Node JS Call GRPC Server with custom headers
body: <p>I am trying to call a GRPC endpoint but I want to provide a customer auth header. Where do I specify this?    </p>
  
  <pre><code>var client = new proto.Publisher('127.0.0.1:50051',
      grpc.credentials.createInsecure());
  
  var customHeader = { 
      'authorization': 'secret'
  }
  
  client.publish(data, function (err, response) {
    console.log('Sent');
  });
  </code></pre>