slack.util.js

const joinSlackChannel = (channel, message = null) => {
    return new Promise(async (resolve, reject) => {
        try {
            const resp = await web.conversations.join({
                channel: channel,
            });
            if (message) {
                await sendSlackMessage(message, channel);
            }
            return resolve(true);
        } catch (error) {
            return resolve(true);
        }
    });
};