Fix compile errors

client.go

@@ -53,7 +53,7 @@ func (c *Client) Do(msg *Msg, addr string, data interface{}, callback func(*Msg,
 }
 
 // DoRtt is equivalent to Do, except that is calls ExchangeRtt.
-func (c *Client) Do(msg *Msg, addr string, data interface{}, callback func(*Msg, *Msg, rtt time.Duration, error, interface{})) {
+func (c *Client) DoRtt(msg *Msg, addr string, data interface{}, callback func(*Msg, *Msg, time.Duration, error, interface{})) {
 	go func() {
 		r, rtt, err := c.ExchangeRtt(msg, addr)
 		callback(msg, r, rtt, err, data)

dns.go

@@ -65,7 +65,6 @@ package dns
 import (
 	"net"
 	"strconv"
-	"time"
 )
 
 const (

xfr.go

@@ -1,5 +1,10 @@
 package dns
 
+import (
+	"net"
+	"time"
+)
+
 // XfrReceives requests an incoming Ixfr or Axfr. If the message q's question
 // section has type TypeAXFR an Axfr is performed, if it is TypeIXFR it does an Ixfr.
 // The [AI]xfr's records are returned on the channel. Note that with an IXFR the client