Resolve lua module path with slash.

[deflinhec]

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[zyro]

@deflinhec Thanks for the PR! Could you add a bit of detail on what the issue you're trying to solve is, example(s) of prior behaviour, and example(s) of behaviour after your PR would be applied?

[deflinhec]

lua 5.1 open package treats . as /. So require("base.utils") should equivalent to require("base/utils").

[deflinhec]

I was porting some lua files from different project into Nakama module directory and errors shown right after server restart.

{"level":"info","ts":"2021-09-02T16:33:24.755Z","caller":"server/runtime_lua.go:111","msg":"Initialising Lua runtime provider","path":"data/modules"}
{"level":"error","ts":"2021-09-02T16:33:24.766Z","caller":"server/runtime_lua.go:1955","msg":"Could not complete runtime invocation","error":"data/modules/lobby/rpc.lua:15: module base/util not found:\n\tno field package.preload['base/util']\n\tno cached module 'base/util', \nstack traceback:\n\t[G]: in function 'require'\n\tdata/modules/lobby/rpc.lua:15: in main chunk\n\t[G]: ?"}
{"level":"error","ts":"2021-09-02T16:33:24.766Z","caller":"server/runtime.go:590","msg":"Error initialising Lua runtime provider","error":"data/modules/lobby/rpc.lua:15: module base/util not found:\n\tno field package.preload['base/util']\n\tno cached module 'base/util', \nstack traceback:\n\t[G]: in function 'require'\n\tdata/modules/lobby/rpc.lua:15: in main chunk\n\t[G]: ?"}
{"level":"fatal","ts":"2021-09-02T16:33:24.767Z","caller":"v3/main.go:148","msg":"Failed initializing runtime modules","error":"data/modules/lobby/rpc.lua:15: module base/util not found:\n\tno field package.preload['base/util']\n\tno cached module 'base/util', \nstack traceback:\n\t[G]: in function 'require'\n\tdata/modules/lobby/rpc.lua:15: in main chunk\n\t[G]: ?"}

After removing dependency between files, I'm also confuse with this log message. All modules has been load correctly, but not found when requiring them.

{"level":"info","ts":"2021-09-02T15:34:23.824Z","caller":"server/runtime.go:611","msg":"Found runtime modules","count":3,"modules":["base/util.lua","lobby/control.lua","lobby/rpc.lua"]}

Then I found that all lua module stores in moduleCache converts / to ..