code: func (r *MemoryTTL) Set(key string, value interface{}) error {
  	r.Lock()
  	defer r.Unlock()
  
  	r.cache.Set(key, value)
  	r.setAts[key] = time.Now()
  	return nil
  }
docs: // Set will persist a value to the cache or
  // override existing one with the new one