calling lua scripts from goroutines

lua.go

package main

import (
    "github.com/yuin/gopher-lua"
    "fmt"
)

const debug = false
const count = 10

func lstate() *lua.LState {
	L := lua.NewState()
	L.OpenLibs()
	L.Register("go", goroutine)
	L.SetGlobal("debug", debug && lua.LTrue || lua.LFalse)
	L.SetGlobal("count", lua.LNumber(10))
	return L
}

func goroutine(l *lua.LState) int {
    fn := l.ToFunction(1)

	vars := l.GetTop() - 1
	values := make([]lua.LValue, vars)
	for i := 0; i<vars; i += 1 {
		values[i] = l.Get(i+2)
	}

    go func() {
		L := lstate()
		defer L.Close()
		co := L.NewThread()
		for {
			st, err, values := L.Resume(co, fn, values...)
			if st == lua.ResumeError {
				fmt.Println("yield break(error)")
				fmt.Println(err.Error())
				break
			}

			if debug {
				for i, lv := range values {
					fmt.Printf("%v : %v\n", i, lv)
				}
			}

			if st == lua.ResumeOK {
				break
			}
		}
	}()

    return 0
}

func callLua(script string) interface{} {
	L := lstate()
    defer L.Close()
    err := L.DoString(script)
    if err != nil {
        panic(err)
    }
    return L.ToInt(1)
}

func main() {
    script := `
local ch = channel.make()

local t = { x = 3 }
for i = 1, count do
	go(function(table)
		if debug then print(table) end
		assert(table.x == t.x, "table field")
		ch:send(i)
		coroutine.yield(i)
		return i
	end, t)
end

local sum = 0
local done = count
repeat
	channel.select({"|<-", ch,
			function(ok, data)
				sum = sum + data
				done = done - 1
			end
	})
until done == 0
ch:close()

return sum
`
	res := callLua(script).(int)
	expect := 0
	for i := 1; i <= count; i += 1 {
		expect += i
	}
	if res != expect {
		panic(fmt.Sprintf("WTF? %d != %d", res, expect))
	}
}