在用春哥写的lua的 upload.lua 模块时一直报错，求大神指导
2014/11/17 09:47:41 [error] 16933#0: *1 lua entry thread aborted: runtime error: /usr/upload.lua:23: attempt to call method 'read' (a nil value)
stack traceback:
coroutine 0:
/usr/upload.lua: in function </usr/upload.lua:1>, client: 10.10.3.35, server: 10.10.3.253, request: "POST /uploadfile HTTP/1.1", host: "10.10.3.253", referrer: "
http://10.10.3.253/"
