Preventing the fail of the 'ETIMEDOUT' code in 500 'Internal server error' (chimurai#480)

Thanks for this PR!

Author: aremishevsky

src/handlers.ts

@@ -54,6 +54,7 @@ function defaultErrorHandler(err, req, res) {
         case 'ECONNRESET':
         case 'ENOTFOUND':
         case 'ECONNREFUSED':
+        case 'ETIMEDOUT':
           res.writeHead(504);
           break;
         default:

test/unit/handlers.spec.ts

@@ -104,6 +104,7 @@ describe('default proxy error handler', () => {
     ['ECONNREFUSED', 504],
     ['ENOTFOUND', 504],
     ['ECONNREFUSED', 504],
+    ['ETIMEDOUT', 504],
     ['any', 500],
   ];