fastip: fix type

fastip/ping.go

@@ -21,7 +21,7 @@ type pingResult struct {
 	// ipp is the address-port pair the result is related to.
 	ipp netutil.IPPort
 	// latency is the duration of dialing process in milliseconds.
-	latency time.Duration
+	latency uint
 	// success is true when the dialing succeeded.
 	success bool
 }