feat: mv internal/pkg to root [skip ci]

pkg/pubsub/pubsub.go

@@ -0,0 +1,27 @@
+package pubsub
+
+import "context"
+
+type Subject string
+
+func (subject Subject) String() string {
+	return string(subject)
+}
+
+type Message interface{}
+
+type Publishing struct{}
+
+type PublishOption func(*Publishing)
+
+type Publisher interface {
+	Publish(context.Context, Subject, Message, ...PublishOption) error
+}
+
+type MessageHandler interface {
+	HandleMessage(context.Context, *Message) error
+}
+
+type Subscriber interface {
+	Subscribe(context.Context, Subject, MessageHandler) error
+}