Update gomod and vendor

vendor/github.com/moby/buildkit/solver/cachekey.go

@@ -0,0 +1,66 @@
+package solver
+
+import (
+	"sync"
+
+	digest "github.com/opencontainers/go-digest"
+)
+
+// NewCacheKey creates a new cache key for a specific output index
+func NewCacheKey(dgst digest.Digest, output Index) *CacheKey {
+	return &CacheKey{
+		ID:     rootKey(dgst, output).String(),
+		digest: dgst,
+		output: output,
+		ids:    map[*cacheManager]string{},
+	}
+}
+
+// CacheKeyWithSelector combines a cache key with an optional selector digest.
+// Used to limit the matches for dependency cache key.
+type CacheKeyWithSelector struct {
+	Selector digest.Digest
+	CacheKey ExportableCacheKey
+}
+
+type CacheKey struct {
+	mu sync.RWMutex
+
+	ID     string
+	deps   [][]CacheKeyWithSelector // only [][]*inMemoryCacheKey
+	digest digest.Digest
+	output Index
+	ids    map[*cacheManager]string
+
+	indexIDs []string
+}
+
+func (ck *CacheKey) Deps() [][]CacheKeyWithSelector {
+	ck.mu.RLock()
+	defer ck.mu.RUnlock()
+	deps := make([][]CacheKeyWithSelector, len(ck.deps))
+	for i := range ck.deps {
+		deps[i] = append([]CacheKeyWithSelector(nil), ck.deps[i]...)
+	}
+	return deps
+}
+
+func (ck *CacheKey) Digest() digest.Digest {
+	return ck.digest
+}
+func (ck *CacheKey) Output() Index {
+	return ck.output
+}
+
+func (ck *CacheKey) clone() *CacheKey {
+	nk := &CacheKey{
+		ID:     ck.ID,
+		digest: ck.digest,
+		output: ck.output,
+		ids:    map[*cacheManager]string{},
+	}
+	for cm, id := range ck.ids {
+		nk.ids[cm] = id
+	}
+	return nk
+}