local error = error
local ERROR = "error"
local kong = kong
local _M = {}
local funtion do_authentication(conf)
    if not kong.request.get_header("token") then
        return nil,{
            status = 401,
            message = {
                [ERROR] = "invalid_request",
                error_description = "The token is missing"
           headers = {
               ["WWW-Authenticate"] = "example"
fuction _M.execute(conf)
    local ok,err = do_authentication(conf)
    if not ok then
        return kong.response.error(err.status, err.message, err.headers)
return _M
When I test it ,I got a unexception error,and the error log is message must be a nil or a string, I change the message to a string and run success.

but in the pdk source code 981 I found the message can use table so what's wrong with my code?
          
Hello, could it be that you forgot to add a return true to do_authentication? Otherwise, if the expected header is passed, the function will return nil, nil, provoking an error log similar to the one you are getting.
If that's not it, could you please provide us with a more detailed trace of the error?
Hello, could it be that you forgot to add a return true to do_authentication? Otherwise, if the expected header is passed, the function will return nil, nil, provoking an error log similar to the one you are getting.
If that's not it, could you please provide us with a more detailed trace of the error?
I just test the condition of token missing.

And here is the log
2021/05/10 15:27:34 [error] 26574#0: *3913 [kong] init.lua:271 [sso] /data/code/kong-plugin-sso/kong/plugins/sso/handler.lua:9: message must be a nil or a string, client: 10.132.106.37, server: kong, request: "GET /RdTestLoginService/actuator/health HTTP/1.1", host: "10.114.205.170:8000"
and the handle.lua :
local access = require "kong.plugins.sso.access"
local SSOHandler = {PRIORITY = 1000,VERSION="1.0.0"}
funtion SSOHandler:access(conf)
    access.excute(conf)
return SSOHandler
and I try to use cjson format the table to string :
fuction _M.execute(conf)
    local ok,err = do_authentication(conf)
    if not ok then
         local jsonMessage,jsonError = cjson.encode(err.massage)
        return kong.response.error(err.status, jsonMessage, err.headers)
It work fine.
          
Hi @FaustPipeDream!
The support for the "table" type message in kong.response.error() will be part of the next Kong release. The code you mentioned is in the master branch but is not part of Kong 2.4.0 (or even 2.4.1, FWIW). If you check Kong 2.4.0, kong.response.error() doesn't handle tables: https://github.com/Kong/kong/blob/2.4.0/kong/pdk/response.lua#L984
As this is an actual issue but already fixed, I'm closing this ticket. Thanks for your report!