【Lua实战】goto状态清理：多层循环退出的资源回收写法

local function processBatch(tasks)
    local done, err = 0, nil
    for _, group in ipairs(tasks) do
        for _, task in ipairs(group) do
            if done >= 200 then
                err = "batch_full"
                goto cleanup
            end
            if task.item == nil then
                err = "bad_task:" .. tostring(task.id)
                goto cleanup
            end
            done = done + 1
        end
    end
    ::cleanup::
    setsysvar("BATCH_LAST", done .. "|" .. tostring(err))
    return err == nil, err
end

local function finishBatch(handle)
    ::cleanup::
    if handle ~= nil then
        releaseHandle(handle)
    end
    setsysvar("BATCH_STATE", "closed")
end