code: func (c *DiskTokenCache) DeleteToken(key *CacheKey) error {
  	return c.updateCacheFile(func(cache *cacheFile, now time.Time) bool {
  		for i, entry := range cache.Cache {
  			if EqualCacheKeys(&entry.Key, key) {
  				cache.Cache = append(cache.Cache[:i], cache.Cache[i+1:]...)
  				return true
  			}
  		}
  		return false // not there, this is fine, skip writing the file
  	})
  }
docs: // DeleteToken removes the token from cache.