lua: error loading module 'cjson' from file '/usr/local/lib/lua/5.3/cjson.so':
        dlopen(/usr/local/lib/lua/5.3/cjson.so, 6): Symbol not found: _lua_objlen
  Referenced from: /usr/local/lib/lua/5.3/cjson.so
  Expected in: flat namespace
 in /usr/local/lib/lua/5.3/cjson.so
stack traceback:
        [C]: in ?
        [C]: in function 'require'
        log.lua:6: in main chunk
        [C]: in ?

$ luarocks remove lua-cjson
$ luarocks install lua-cjson 2.1.0-1

　　https://github.com/mpx/lua-cjson/issues/56