Pass a map (or concurrent hashmap) in a DoFn(apache crunch)

Question

Since there's a limit for Hadoop counter size(and we dont want to increase it for just one job), I am creating a map(Map) which will increment the key if some conditions are met(Same as counters). There is already a DoFn (returning custom made object) which is processing the data so I am interested in passing a map into it and grouping it outside based on keys. I think concurrenthashmap might work but unable to implement the same.