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

mdns.go

@@ -0,0 +1,117 @@
+// Package mdns is an mdns router
+package mdns
+
+import (
+	"fmt"
+	"net"
+	"strconv"
+	"time"
+
+	"github.com/micro/go-micro/v3/router"
+	"github.com/micro/go-micro/v3/util/mdns"
+)
+
+// NewRouter returns an initialized dns router
+func NewRouter(opts ...router.Option) router.Router {
+	options := router.DefaultOptions()
+	for _, o := range opts {
+		o(&options)
+	}
+	if len(options.Network) == 0 {
+		options.Network = "micro"
+	}
+	return &mdnsRouter{options}
+}
+
+type mdnsRouter struct {
+	options router.Options
+}
+
+func (m *mdnsRouter) Init(opts ...router.Option) error {
+	for _, o := range opts {
+		o(&m.options)
+	}
+	return nil
+}
+
+func (m *mdnsRouter) Options() router.Options {
+	return m.options
+}
+
+func (m *mdnsRouter) Table() router.Table {
+	return nil
+}
+
+func (m *mdnsRouter) Lookup(opts ...router.QueryOption) ([]router.Route, error) {
+	options := router.NewQuery(opts...)
+
+	// check to see if we have the port provided in the service, e.g. go-micro-srv-foo:8000
+	service, port, err := net.SplitHostPort(options.Service)
+	if err != nil {
+		service = options.Service
+	}
+
+	// query for the host
+	entries := make(chan *mdns.ServiceEntry)
+
+	p := mdns.DefaultParams(service)
+	p.Timeout = time.Millisecond * 100
+	p.Entries = entries
+
+	// check if we're using our own network
+	if len(options.Network) > 0 {
+		p.Domain = options.Network
+	}
+
+	// do the query
+	if err := mdns.Query(p); err != nil {
+		return nil, err
+	}
+
+	var routes []router.Route
+
+	// compose the routes based on the entries
+	for e := range entries {
+		addr := e.Host
+		// prefer ipv4 addrs
+		if len(e.AddrV4) > 0 {
+			addr = e.AddrV4.String()
+			// else use ipv6
+		} else if len(e.AddrV6) > 0 {
+			addr = "[" + e.AddrV6.String() + "]"
+		} else if len(addr) == 0 {
+			continue
+		}
+
+		pt := 443
+
+		if e.Port > 0 {
+			pt = e.Port
+		}
+
+		// set the port
+		if len(port) > 0 {
+			pt, _ = strconv.Atoi(port)
+		}
+
+		routes = append(routes, router.Route{
+			Service: service,
+			Address: fmt.Sprintf("%s:%d", addr, pt),
+			Network: p.Domain,
+		})
+	}
+
+	return routes, nil
+}
+
+func (m *mdnsRouter) Watch(opts ...router.WatchOption) (router.Watcher, error) {
+	return nil, nil
+}
+
+func (m *mdnsRouter) Close() error {
+	return nil
+}
+
+func (m *mdnsRouter) String() string {
+	return "mdns"
+}