Add doppel and tls packages

mtglib/internal/doppel/clock.go

@@ -0,0 +1,35 @@
+package doppel
+
+import (
+	"context"
+	"time"
+)
+
+type Clock struct {
+	stats *Stats
+	tick  chan struct{}
+}
+
+func (c Clock) Start(ctx context.Context) {
+	tickTock := time.NewTimer(c.stats.Delay())
+	defer func() {
+		tickTock.Stop()
+		select {
+		case <-tickTock.C:
+		default:
+		}
+	}()
+
+	for {
+		select {
+		case <-ctx.Done():
+			return
+		case <-tickTock.C:
+			select {
+			case <-ctx.Done():
+			case c.tick <- struct{}{}:
+			}
+			tickTock.Reset(c.stats.Delay())
+		}
+	}
+}