Update connection delay issue (#10359)

* Update connection delay issue

There needs to be a delay after the connection is started. The old sample code did not allow for this and caused errors in the application.

* Disabled Send Button Until Connection Established

Disabled Send Button Until Connection Established

* Moved sendButton listener outside of then function

Moved sendButton listener outside of then function

aspnetcore/tutorials/signalr/sample/wwwroot/js/chat.js

@@ -2,6 +2,9 @@
 
 var connection = new signalR.HubConnectionBuilder().withUrl("/chatHub").build();
 
+//Disable send button until connection is established
+document.getElementById("sendButton").disabled = true;
+
 connection.on("ReceiveMessage", function (user, message) {
     var msg = message.replace(/&/g, "&amp;").replace(/</g, "&lt;").replace(/>/g, "&gt;");
     var encodedMsg = user + " says " + msg;
@@ -10,7 +13,9 @@ connection.on("ReceiveMessage", function (user, message) {
     document.getElementById("messagesList").appendChild(li);
 });
 
-connection.start().catch(function (err) {
+connection.start().then(function(){
+    document.getElementById("sendButton").disabled = false;
+}).catch(function (err) {
     return console.error(err.toString());
 });
 
@@ -21,4 +26,4 @@ document.getElementById("sendButton").addEventListener("click", function (event)
         return console.error(err.toString());
     });
     event.preventDefault();
-});
+});