I'm using a hook to write the logs to graylog using GELF client ( "gopkg.in/Graylog2/go-gelf.v2/gelf") it appears that there is no way to access with fields like ``` log.With().Str("k","v).Logger().Info().Msg("some message") ``` I want to add the `k` as extra field (with its value as `v`) in GELF message. is there a way we can do this?