fix ipv6 addr parsing and using

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

transport/http_transport_test.go

@@ -2,14 +2,16 @@ package transport
 
 import (
 	"io"
-	"strings"
+	"net"
 	"testing"
 	"time"
 )
 
 func expectedPort(t *testing.T, expected string, lsn Listener) {
-	parts := strings.Split(lsn.Addr(), ":")
-	port := parts[len(parts)-1]
+	_, port, err := net.SplitHostPort(lsn.Addr())
+	if err != nil {
+		t.Errorf("Expected address to be `%s`, got error: %v", expected, err)
+	}
 
 	if port != expected {
 		lsn.Close()