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)
+	}
+}

router/service/service.go

@@ -36,9 +36,10 @@ func NewRouter(opts ...router.Option) router.Router {
 	// NOTE: might need some client opts here
 	cli := client.DefaultClient
 
-	// set options client
-	if options.Client != nil {
-		cli = options.Client
+	// get options client from the context. We set this in the context to prevent an import loop, as
+	// the client depends on the router
+	if c, ok := options.Context.Value(clientKey{}).(client.Client); ok {
+		cli = c
 	}
 
 	// NOTE: should we have Client/Service option in router.Options?