v3 refactor (#1868)

* Move to v3

Co-authored-by: Ben Toogood <bentoogood@gmail.com>

watcher.go

@@ -0,0 +1,52 @@
+package registry
+
+import (
+	"sync"
+
+	"github.com/micro/go-micro/v3/router"
+)
+
+// tableWatcher implements routing table Watcher
+type tableWatcher struct {
+	sync.RWMutex
+	id      string
+	opts    router.WatchOptions
+	resChan chan *router.Event
+	done    chan struct{}
+}
+
+// Next returns the next noticed action taken on table
+// TODO: right now we only allow to watch particular service
+func (w *tableWatcher) Next() (*router.Event, error) {
+	for {
+		select {
+		case res := <-w.resChan:
+			switch w.opts.Service {
+			case res.Route.Service, "*":
+				return res, nil
+			default:
+				continue
+			}
+		case <-w.done:
+			return nil, router.ErrWatcherStopped
+		}
+	}
+}
+
+// Chan returns watcher events channel
+func (w *tableWatcher) Chan() (<-chan *router.Event, error) {
+	return w.resChan, nil
+}
+
+// Stop stops routing table watcher
+func (w *tableWatcher) Stop() {
+	w.Lock()
+	defer w.Unlock()
+
+	select {
+	case <-w.done:
+		return
+	default:
+		close(w.done)
+	}
+}