How to set ObjectId for nested document in golang?

Model:

type Vehicle   struct {
    Id          bson.ObjectId `bson:"_vid,omitempty"`
	Brand			string
	Category		string	
	CategorySubject		string
	MakeYear 		string
	RegistrationNumber	string
	Model			string
	Price			string
}
func (this *Vehicle)AddToDB(emailId1 string)  {
    sess, db := GetDatabase()
	defer sess.Close()
	c := db.C("user")
	//newId :=Vehicle{}
	/*colQuerier := bson.M{"email": person.Email}
	change := bson.M{"$set": bson.M{"profile" : imgName}}
	err = c.Update(colQuerier, change)*/
	colQuerier := bson.M{"email": emailId1}
	change := bson.M{"$push": bson.M{"myvehicle" : &this}}
	err := c.Update(colQuerier, change)
	if err != nil {
		fmt.Println("not inserted")	
	}
}

The value of Id of Vehicle is empty when it's pushed into myvehicle field.

How do I set a value for the nested Vehicle's id ?

MongoDB ObjectId is auto inserted for document (not sub-document) that does not specify _id field. This is to uniquely identify the document.

In your case above, if you are inserting a nested object (sub-document) the Id field would not be auto-inserted by MongoDB.

You can however create an ObjectId (unique identifier) for the newly pushed Vehicle document. For example:

new_object_id := bson.NewObjectId()

See also NewObjectId