improve eventbus

examples/eventbus/modules/some_module/some_module.v

@@ -13,19 +13,22 @@ pub struct Work {
 	hours int
 }
 
+pub struct Error {
+	pub:
+	message string
+}
+
 pub fn do_work(){
 	work := Work{20}
-	mut params := eventbus.Params{}
 	for i in 0..20 {
 		println("working...")
 		if i == 15 {
-			params.put_string("error", "CRASH!!")
-			eb.publish("error", work, params)
-			eb.publish("error", work, params)
+			error := &Error{"There was an error."}
+			eb.publish("error", work, error)
+			eb.publish("error", work, error)
 			return
 		}
 	}
-	
 }
 
 pub fn get_subscriber() eventbus.Subscriber {