使用bson的golang结构默认值

I looking return default value for new struct, without value, this is my current struct :

// Campaign represents a email campaign
type Campaign struct {
    ID             bson.ObjectId   `json:"id" bson:"_id"`
    CampaignName   string          `json:"campaign_name" bson:"campaign_name"`
    FromName       []string        `json:"from_name" bson:"from_name"`
    FromEmail      string          `json:"from_email" bson:"from_email"`
    ReplyEmail     string          `json:"reply_email" bson:"reply_email"`
    Subject        []string        `json:"subject" bson:"subject"`
    BodyText       string          `json:"body_text" bson:"body_text"`
    BodyHTML       string          `json:"body_html" bson:"body_html"`
    SMTPList       bson.ObjectId `json:"smtp_list" bson:"smtp_list"`
    EmailList      bson.ObjectId `json:"email_list" bson:"email_list"`
    DateCreated    time.Time       `json:"date_created" bson:"date_created"`
    DateUpdated    time.Time       `json:"date_updated" bson:"date_updated"`
    DateSendFinish time.Time       `json:"date_send_finish" bson:"date_send_finish"`
    OwnerID        bson.ObjectId   `json:"owner_id" bson:"owner_id"`
    Opens          int             `json:"opens" bson:"opens"`
    Clicks         int             `json:"clicks" bson:"clicks"`
    Status         string          `json:"status" bson:"status"`
}

I want to return Status = "draft" How i can do this ?