code: func (c *Client) Increment(key string, delta uint64) (newValue uint64, err error) {
  	return c.incrDecr(cmdIncr, key, delta)
  }
docs: // Increment atomically increments key by delta. The return value is
  // the new value after being incremented or an error. If the value
  // didn't exist in memcached the error is ErrCacheMiss. The value in
  // memcached must be an decimal number, or an error will be returned.
  // On 64-bit overflow, the new value wraps around.