Similar to #4, map (aka record, struct, object) types should be supported. The keys should always be strings, but the values can be customizable. The two separators should be configurable.

{
  debug: g.map(g.string()),
  extraHeaders: g.map(string()).delimiters({field: ";", value: ":"}),
}

and the matching env

LOG="http=error,fs=warn,db=info"
EXTRA_HEADERS="Cache-Control: public; X-Custom-Header: cool-cats"