BUG: The expiration time may not take effect

[Mhaoyuan]

lrucache:set(key, value, ttl, flags)
os.execute("sleep " .. tonumber(ttl+2))
local data, stale_data, flags = lrucache:get(key)
data is not nil

lruchache' get method
if node.expire >= 0 and node.expire < ngx_now() then
return nil, val, node.user_flags
end

ngx_now() Returns a floating-point number for the elapsed time in seconds (including milliseconds as the decimal part) from the epoch for the current time stamp from the Nginx cached time (no syscall involved unlike Lua's date library). https://github.com/openresty/lua-nginx-module#ngxnow

Is it better to add an ngx.update_time()？