router: add to service options; add dns and static implementations (#1733)

* config/cmd: add router to service options

* router/service: use micro client

router/service/options.go

@@ -0,0 +1,22 @@
+package service
+
+import (
+	"context"
+
+	"github.com/micro/go-micro/v2/client"
+	"github.com/micro/go-micro/v2/router"
+)
+
+type clientKey struct{}
+
+// Client to call router service
+func Client(c client.Client) router.Option {
+	return func(o *router.Options) {
+		if o.Context == nil {
+			o.Context = context.WithValue(context.Background(), clientKey{}, c)
+			return
+		}
+
+		o.Context = context.WithValue(o.Context, clientKey{}, c)
+	}
+}