gistfile1.lua

-- list of headers where tables are allowed
local ALLOWED_MULTI_HEADERS = {
   ["cookie"] = true,
}

local function sanitize_req_headers(req_headers)

   for k, v in pairs(req_headers) do
      if type(v) == "table" then
         if not ALLOWED_MULTI_HEADERS[k] then
            req_headers[k] = v[1]
         end
      end
   end

   return req_headers
end

ngx.req.get_headers = function ()
  return sanitize_req_headers(ngx_req_get_headers())
end