attempt to call field 'say' (a nil value)

follower this find error :
https://openresty.org/cn/using-luarocks.html

ERROR:

tail -f /usr/local/openresty/nginx/logs/error.log

2019/11/04 18:31:48 [error] 2028#2028: *2 lua entry thread aborted: runtime error: content_by_lua(nginx.conf:68):3: attempt to call field 'say' (a nil value)
stack traceback:
coroutine 0:
	content_by_lua(nginx.conf:68): in main chunk, client: 127.0.0.1, server: localhost, request: "GET /luarocks HTTP/1.1", host: "localhost"

nginx.conf

    64	        location = /luarocks {
    65	            content_by_lua '
    66	                local foo = require("foo")
    67	                foo.say("hello, luarocks!")
    68	            ';
    69	        }
    70	

Start with the content_by_lua block in nginx.conf at lines 64-69 and compare it with the linked LuaRocks/OpenResty example. Reproduce the GET /luarocks request while checking the reported error log and the foo module setup. The issue gives no acceptance condition, so completion requires confirming the intended behavior and the cause of the missing say field.