package model import ( "encoding/json" "time" ) type Invoice struct { ID int OrderNo string Header string TaxNumber string Order *Order `gorm:"foreignKey:OrderNo;references:OrderNo"` CreatedAt time.Time UpdatedAt time.Time `json:"-"` } func (Invoice) TableName() string { return "invoice" } func (a Invoice) MarshalJSON() ([]byte, error) { type Alias Invoice return json.Marshal(&struct { CreatedAt string UpdatedAt string *Alias }{ CreatedAt: a.CreatedAt.Format("2006-01-02 15:04:05"), UpdatedAt: a.UpdatedAt.Format("2006-01-02 15:04:05"), Alias: (*Alias)(&a), }) }