cleanup client/selector/lookup (#1937)

* cleanup client/selector/lookup

* add mdns router, remove registry from client

* fix roundtripper

* remove comment

* fix compile issue

* fix mucp test

* fix api router

selector/random/random.go

@@ -1,10 +1,44 @@
 package random
 
 import (
+	"math/rand"
+
 	"github.com/micro/go-micro/v3/selector"
 )
 
+type random struct{}
+
+func (r *random) Select(routes []string, opts ...selector.SelectOption) (selector.Next, error) {
+	// we can't select from an empty pool of routes
+	if len(routes) == 0 {
+		return nil, selector.ErrNoneAvailable
+	}
+
+	// return the next func
+	return func() string {
+		// if there is only one route provided we'll select it
+		if len(routes) == 1 {
+			return routes[0]
+		}
+
+		// select a random route from the slice
+		return routes[rand.Intn(len(routes)-1)]
+	}, nil
+}
+
+func (r *random) Record(addr string, err error) error {
+	return nil
+}
+
+func (r *random) Reset() error {
+	return nil
+}
+
+func (r *random) String() string {
+	return "random"
+}
+
 // NewSelector returns a random selector
 func NewSelector(opts ...selector.Option) selector.Selector {
-	return selector.DefaultSelector
+	return new(random)
 }