examples: improve the sendbus example (#13604)

examples/eventbus/eventbus.v

@@ -2,12 +2,32 @@ module main
 
 import some_module
 
-fn main() {
-	mut sub := some_module.get_subscriber()
-	sub.subscribe('error', on_error)
-	some_module.do_work()
+struct Receiver {
+mut:
+	ok bool
 }
 
-fn on_error(sender voidptr, e &some_module.MyError, x voidptr) {
-	println(e.message)
+fn main() {
+	mut sub := some_module.get_subscriber()
+	r := Receiver{}
+	sub.subscribe_method('event_foo', on_foo, r)
+	sub.subscribe('event_bar', on_bar)
+	sub.subscribe('event_baz', on_baz)
+
+	println('Receiver ok: ' + r.ok.str())
+	some_module.do_work()
+	println('Receiver ok: ' + r.ok.str())
+}
+
+fn on_foo(mut receiver Receiver, e &some_module.EventMetadata, sender voidptr) {
+	receiver.ok = true
+	println('on_foo :: ' + e.message)
+}
+
+fn on_bar(receiver voidptr, e &some_module.EventMetadata, sender voidptr) {
+	println('on_bar :: ' + e.message)
+}
+
+fn on_baz(receiver voidptr, event voidptr, d &some_module.Duration) {
+	println('on_baz :: ' + d.hours.str())
 }