# output all HTTP header as received by nginx
location /header {
 default_type 'text/plain';
 content_by_lua_block {
  local myheads=ngx.req.get_headers()
  for key in pairs(myheads) do
   local outp="Header '" .. key .. "': " .. myheads[key]
   ngx.say(outp)
  end
 }
}