copy the reader, otherwise it will get drained by the first JSON-marshaling
try
truly copy the io.Reader to consume it twice
use the appropriate type for json de-serialisation
immediately bind to port

If port binding takes too long, the app will fail on Heroku
revert change on how to assemble string of categorizations
fix typo
go fmt
also check for valid portal url starting with uri://data.
add test files