Imports of package cachecheck

PathSynopsis
github.com/docker/distributionPackage distribution will define the interfaces for the components of docker distribution.
github.com/docker/distribution/contextPackage context provides several utilities for working with Go's context in http requests.
github.com/docker/distribution/digest
github.com/docker/distribution/registry/storage/cachePackage cache provides facilities to speed up access to the storage backend.
reflectPackage reflect implements run-time reflection, allowing a program to manipulate objects with arbitrary types.
testingPackage testing provides support for automated testing of Go packages.