code: func SetDecoder(decoder Decoder) ClientOptionFunc {
  	return func(c *Client) error {
  		if decoder != nil {
  			c.decoder = decoder
  		} else {
  			c.decoder = &DefaultDecoder{}
  		}
  		return nil
  	}
  }
docs: // SetDecoder sets the Decoder to use when decoding data from Elasticsearch.
  // DefaultDecoder is used by default.