migrate to go modules

Signed-off-by: Valentin Rothberg <rothberg@redhat.com>

vendor/github.com/Microsoft/hcsshim/internal/wclayer/layerid.go

@@ -0,0 +1,13 @@
+package wclayer
+
+import (
+	"path/filepath"
+
+	"github.com/Microsoft/hcsshim/internal/guid"
+)
+
+// LayerID returns the layer ID of a layer on disk.
+func LayerID(path string) (guid.GUID, error) {
+	_, file := filepath.Split(path)
+	return NameToGuid(file)
+}