How to Automatically Populate Created_at and Updated_at Fields in MongoDB using Go\'s BSON Marshaler?

Automated Creation of Created_at and Updated_at Fields in MongoDB Using the Go Database Driver

In Go, when using the MongoDB database driver, the created_at and updated_at fields in a struct are not automatically populated with timestamps during insertions. To resolve this issue, a custom marshaler can be implemented to update these fields before saving the struct to MongoDB.

type User struct {
    ID           primitive.ObjectID `bson:"_id,omitempty"`
    CreatedAt    time.Time          `bson:"created_at"`
    UpdatedAt    time.Time          `bson:"updated_at"`
    Name         string             `bson:"name"`
}

func (u *User) MarshalBSON() ([]byte, error) {
    if u.CreatedAt.IsZero() {
        u.CreatedAt = time.Now()
    }
    u.UpdatedAt = time.Now()

    type my User
    return bson.Marshal((*my)(u))
}

The MarshalBSON() method is called when saving values of the *User type and ensures that the created_at and updated_at fields are set to the current time before marshaling the object into a BSON representation.

To use this custom marshaler, instantiate a pointer to your User object and insert it into the MongoDB collection:

user := &User{Name: "username"}

c := client.Database("db").Collection("collection")
if _, err := c.InsertOne(context.Background(), user); err != nil {
    // handle error
}

By implementing the MarshalBSON() method, you can automatically generate timestamps for the created_at and updated_at fields when saving a Go struct to MongoDB, ensuring the fields are properly populated with the current time.

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