Merge pull request #3 from libp2p/feat/interface

generify options.

interface.go

@@ -10,7 +10,8 @@ var closeEmit struct{}
 type subSettings struct {
 	forcedType reflect.Type
 }
-type SubOption func(*subSettings) error
+
+type SubOption func(interface{}) error
 
 // ForceSubType is a Subscribe option which overrides the type to which
 // the subscription will be done. Note that the evtType must be assignable
@@ -29,7 +30,8 @@ type SubOption func(*subSettings) error
 // cancel, err := eventbus.Subscribe(eventCh, event.ForceSubType(new(Event)))
 // [...]
 func ForceSubType(evtType interface{}) SubOption {
-	return func(s *subSettings) error {
+	return func(settings interface{}) error {
+		s := settings.(*subSettings)
 		typ := reflect.TypeOf(evtType)
 		if typ.Kind() != reflect.Ptr {
 			return errors.New("ForceSubType called with non-pointer type")
@@ -42,7 +44,7 @@ func ForceSubType(evtType interface{}) SubOption {
 type emitterSettings struct {
 	makeStateful bool
 }
-type EmitterOption func(*emitterSettings)
+type EmitterOption func(interface{}) error
 
 // Stateful is an Emitter option which makes makes the eventbus channel
 // 'remember' last event sent, and when a new subscriber joins the