Protractor ShardTestFiles-每个实例的自定义参数不起作用

我正在用量角器做平行测试。问题是我有3个用户，我想量角器自动选择一个免费用户为每个实例

let usersInActions = {};

const users = [
    { username: 'aaa', password: 'aaa'},
    { username: 'bbb', password: 'bbb'},
    { username: 'ccc', password: 'ccc'}
];

let config = {
    capabilities: {
        browserName: 'chrome',
        chromeOptions: {
            args: ['incognito', 'disable-extensions']
        },
        maxInstances: 3,
        shardTestFiles: true
    },
    beforeLaunch: async () => {
        const capabilities = await browser.getCapabilities();
        const sesssionId = capabilities.get('webdriver.remote.sessionid');

        if (!browser.params.usersInActions) {
            browser.params.usersInActions = {};
        }

        const freeUser = users.find(u => {
            return !browser.params.usersInActions[sesssionId];
        });

        usersInActions[sesssionId] = freeUser;

        browser.params.user = freeUser;
    },
    afterLaunch: async () => {
        const capabilities = await browser.getCapabilities();
        const sesssionId = capabilities.get('webdriver.remote.sessionid');

        browser.params.usersInActions[sesssionId]  = null;
    }
};

• 问题是每次调用新实例时都会重置usersInActions。我相信这是量角器的错误