在Mongoose模型中访问req对象

Question

更新模型后，我想在活动集合中插入新文档

MySchema.post('update', function(doc, next) {
    // here i want to access req.user (current logged In user)
    ActivityLog.create({
    collectionType: 'MySchema'
    action: 'updated',
    loggedBy: req.user
}).then(function(activity) {
    return next();
});
 });

ActivityLog是活动架构