Update gomod and vendor

vendor/github.com/moby/buildkit/client/client_windows.go

@@ -0,0 +1,24 @@
+package client
+
+import (
+	"net"
+	"strings"
+	"time"
+
+	winio "github.com/Microsoft/go-winio"
+	"github.com/pkg/errors"
+)
+
+func dialer(address string, timeout time.Duration) (net.Conn, error) {
+	addrParts := strings.SplitN(address, "://", 2)
+	if len(addrParts) != 2 {
+		return nil, errors.Errorf("invalid address %s", address)
+	}
+	switch addrParts[0] {
+	case "npipe":
+		address = strings.Replace(addrParts[1], "/", "\\", -1)
+		return winio.DialPipe(address, &timeout)
+	default:
+		return net.DialTimeout(addrParts[0], addrParts[1], timeout)
+	}
+}