add stream callbacks

pkg/exchange/okex/stream_callbacks.go

@@ -0,0 +1,19 @@
+// Code generated by "callbackgen -type Stream -interface"; DO NOT EDIT.
+
+package okex
+
+import ()
+
+func (s *Stream) OnKline(cb func()) {
+	s.klineCallbacks = append(s.klineCallbacks, cb)
+}
+
+func (s *Stream) EmitKline() {
+	for _, cb := range s.klineCallbacks {
+		cb()
+	}
+}
+
+type StreamEventHub interface {
+	OnKline(cb func())
+}