Can not load emmy_core.dll

[jinq0123]

test.lua:

package.cpath = package.cpath .. ';' .. './?.dll'
local dbg = require('emmy_core')
dbg.tcpConnect('localhost', 9966)

DoFile() returns error:

test.lua:2: module emmy_core not found:
        no field package.preload['emmy_core']
        CreateFile ./emmy_core.lua: The system cannot find the file specified.,
stack traceback:
        [G]: in function 'require'
        test.lua:2: in main chunk
        [G]: ?

emmy_core.dll and test.lua are in the current work dir and lua.exe can run test.lua:

λ lua test.lua
[EMMY]lua version: 51
lua: [Emmy]connection refused
stack traceback:
        [C]: ?
        [C]: ?
        [C]: in function 'tcpConnect'
        test.lua:3: in main chunk
        [C]: ?