pseudo.js

const trySubscribeAction = function(id, action, log) {
    return Promise.resolve()
    .then( () => {
        if (action == "subscribe") {
            return subscribePromise(id);
        } else {
            return unsubscribePromise(id);
        }
    })
    .then( (result) => {
        log.info({result: result}, "Request success");
    })
    .catch( (error) => {
        log.error({error: err}, "Request failed");
    })
}
const subscribe = function(req, res, next) {
    let deviceId = req.params["id"];
    req.log.info({
        id: deviceID,
        action: "subscribe"
    }, "Received request.");
    
    return trySubscribeAction(deviceId, "subscribe");
}