Update gomod and vendor

vendor/github.com/moby/buildkit/session/secrets/secrets.go

@@ -0,0 +1,30 @@
+package secrets
+
+import (
+	"context"
+
+	"github.com/moby/buildkit/session"
+	"github.com/pkg/errors"
+	"google.golang.org/grpc/codes"
+	"google.golang.org/grpc/status"
+)
+
+type SecretStore interface {
+	GetSecret(context.Context, string) ([]byte, error)
+}
+
+var ErrNotFound = errors.Errorf("not found")
+
+func GetSecret(ctx context.Context, c session.Caller, id string) ([]byte, error) {
+	client := NewSecretsClient(c.Conn())
+	resp, err := client.GetSecret(ctx, &GetSecretRequest{
+		ID: id,
+	})
+	if err != nil {
+		if st, ok := status.FromError(errors.Cause(err)); ok && (st.Code() == codes.Unimplemented || st.Code() == codes.NotFound) {
+			return nil, errors.Wrapf(ErrNotFound, "secret %s not found", id)
+		}
+		return nil, errors.WithStack(err)
+	}
+	return resp.Data, nil
+}