Move the network resolver out (#1944)

resolver/dnssrv/dnssrv.go

@@ -0,0 +1,31 @@
+// Package dns srv resolves names to dns srv records
+package dnssrv
+
+import (
+	"fmt"
+	"net"
+
+	"github.com/micro/go-micro/v3/resolver"
+)
+
+// Resolver is a DNS network resolve
+type Resolver struct{}
+
+// Resolve assumes ID is a domain name e.g micro.mu
+func (r *Resolver) Resolve(name string) ([]*resolver.Record, error) {
+	_, addrs, err := net.LookupSRV("network", "udp", name)
+	if err != nil {
+		return nil, err
+	}
+	records := make([]*resolver.Record, 0, len(addrs))
+	for _, addr := range addrs {
+		address := addr.Target
+		if addr.Port > 0 {
+			address = fmt.Sprintf("%s:%d", addr.Target, addr.Port)
+		}
+		records = append(records, &resolver.Record{
+			Address: address,
+		})
+	}
+	return records, nil
+}