implement some gossip options

Signed-off-by: Vasiliy Tolstov <v.tolstov@unistack.org>

registry/gossip/options.go

@@ -3,6 +3,7 @@ package gossip
 import (
 	"context"
 
+	"github.com/hashicorp/memberlist"
 	"github.com/micro/go-micro/registry"
 )
 
@@ -15,3 +16,30 @@ func Secret(k []byte) registry.Option {
 		o.Context = context.WithValue(o.Context, contextSecretKey{}, k)
 	}
 }
+
+type contextAddress struct{}
+
+// Address to bind to - host:port
+func Address(a string) registry.Option {
+	return func(o *registry.Options) {
+		o.Context = context.WithValue(o.Context, contextAddress{}, a)
+	}
+}
+
+type contextConfig struct{}
+
+// Config allow to inject a *memberlist.Config struct for configuring gossip
+func Config(c *memberlist.Config) registry.Option {
+	return func(o *registry.Options) {
+		o.Context = context.WithValue(o.Context, contextConfig{}, c)
+	}
+}
+
+type contextAdvertise struct{}
+
+// The address to advertise for other gossip members - host:port
+func Advertise(a string) registry.Option {
+	return func(o *registry.Options) {
+		o.Context = context.WithValue(o.Context, contextAdvertise{}, a)
+	}
+}