Lua 错误 收集

不存在的变量或者变量没有定义，提示错误

2017/05/02 13:21:45 [error] 100933#0: *22839 lua entry thread aborted: runtime error: /opt/openresty/nginx/conf/lua/rtmp_auth_key.lua:18: attempt to concatenate global 'myhash123' (a nil value)
stack traceback:
coroutine 0:
        /opt/openresty/nginx/conf/lua/rtmp_auth_key.lua: in function </opt/openresty/nginx/conf/lua/rtmp_auth_key.lua:1>, client: 127.0.0.1, server: 127.0.0.1, request: "GET /rtmp_redirect_lua?name=Tinywan123&app=live&call=publish_done HTTP/1.1", host: "localhost:8081"