func Delete(c context.Context, key string) error {
	return singleError(DeleteMulti(c, []string{key}))
}
func Delete(c context.Context, key string) error {
	return singleError(DeleteMulti(c, []string{key}))
}
// Delete deletes the item for the given key.
// ErrCacheMiss is returned if the specified item can not be found.
// The key must be at most 250 bytes in length.