Fix PR comments

Make default sender not public

client.go

@@ -43,7 +43,7 @@ func NewClient(config *ClientConfig) (*Client, error) {
 	}
 
 	if config.Sender == nil {
-		config.Sender = DefaultBuildAndSend
+		config.Sender = defaultBuildAndSend
 	}
 
 	c := &Client{

client_test.go

@@ -74,7 +74,7 @@ func TestClient(t *testing.T) {
 				assert.Equal(t, testSoftware, software.String())
 
 				// just forward to the default sender.
-				return DefaultBuildAndSend(conn, addr, attrs...)
+				return defaultBuildAndSend(conn, addr, attrs...)
 			},
 		}
 		software := stun.NewSoftware(testSoftware)

sender.go

@@ -9,8 +9,8 @@ import (
 // Sender is responsible for building a message and sending it to the given addr.
 type Sender func(conn net.PacketConn, addr net.Addr, attrs ...stun.Setter) error
 
-// DefaultBuildAndSend is a sender default implementation.
-func DefaultBuildAndSend(conn net.PacketConn, dst net.Addr, attrs ...stun.Setter) error {
+// defaultBuildAndSend is a sender default implementation.
+func defaultBuildAndSend(conn net.PacketConn, dst net.Addr, attrs ...stun.Setter) error {
 	msg, err := stun.Build(attrs...)
 	if err != nil {
 		return err

server.go

@@ -80,7 +80,7 @@ func NewServer(config *ServerConfig) *Server {
 	}
 
 	if config.Sender == nil {
-		config.Sender = DefaultBuildAndSend
+		config.Sender = defaultBuildAndSend
 	}
 
 	manager := allocation.NewManager(&allocation.ManagerConfig{

server_test.go

@@ -163,7 +163,7 @@ func TestServer(t *testing.T) {
 
 				assert.Equal(t, testSoftware, software.String())
 				// just forward to the default sender.
-				return DefaultBuildAndSend(conn, addr, attrs...)
+				return defaultBuildAndSend(conn, addr, attrs...)
 			},
 		}
 		software := stun.NewSoftware(testSoftware)