onError 수정

src/main/java/cokr/xit/foundation/web/WebClient.java

@@ -130,7 +130,7 @@ public class WebClient {
 			System.out.println(hresp.body());
 		};
 		private Consumer<Throwable> errorHandler = t -> {
-			System.out.println(t.getMessage());
+			t.printStackTrace(System.err);
 		};
 
 		public Config header(String key, String value) {