github.com/BTBurke/caddy-jwt (go): Flatten makes flat, one-dimensional maps from arbitrarily nested ones.  Map keys turn into compound names, like `a.b.1.c` (dotted style) or `a[b][1][c]` (Rails style).  It takes input as either JSON strings or Go structures.  It (only) knows how to traverse JSON types: maps, slices and scalars.  Or Go maps directly.
Keywords: caddy|caddy-plugin|caddyserver|jwt|middleware