Add Fields type alias to log package

Signed-off-by: Maksym Pavlenko <pavlenko.maksym@gmail.com>

diff/windows/windows.go

@@ -42,7 +42,6 @@ import (
 	"github.com/containerd/containerd/plugin"
 	"github.com/opencontainers/go-digest"
 	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
-	"github.com/sirupsen/logrus"
 )
 
 func init() {
@@ -94,7 +93,7 @@ func (s windowsDiff) Apply(ctx context.Context, desc ocispec.Descriptor, mounts
 	t1 := time.Now()
 	defer func() {
 		if err == nil {
-			log.G(ctx).WithFields(logrus.Fields{
+			log.G(ctx).WithFields(log.Fields{
 				"d":      time.Since(t1),
 				"digest": desc.Digest,
 				"size":   desc.Size,
@@ -295,7 +294,7 @@ func (s windowsDiff) Compare(ctx context.Context, lower, upper []mount.Mount, op
 		Digest:    info.Digest,
 	}
 
-	log.G(ctx).WithFields(logrus.Fields{
+	log.G(ctx).WithFields(log.Fields{
 		"d":     time.Since(t1),
 		"dgst":  desc.Digest,
 		"size":  desc.Size,