Gorm UUID Many to Many

Hasham Ali’s How to Use UUID Key Type with Gorm article was terrific for suggesting how to handle using UUID as the ID in gorm. It took a little more fiddling to be able to use the keys in a many-to-many relationship. In the end, it worked by having to explicitly define the join table and the foreign key constraints. Sample code is below.

import (

// BaseAttributes contains common columns for all tables.
// This will replace the default gorm.Model : https://pkg.go.dev/gorm.io/gorm@v1.25.4#Model
// and in this specific case will replace the uint id type with uuid.
type BaseAttributes struct {
	ID        uuid.UUID  `json:"id" gorm:"type:uuid;primary_key;"`
	CreatedAt time.Time
	UpdatedAt time.Time
	DeletedAt *time.Time `sql:"index"`

// BeforeCreate is a gorm hook to auto-set a UUID at objection creation time.
// https://gorm.io/docs/hooks.html
func (base *BaseGormUUID) BeforeCreate(tx *gorm.DB) error {
	tx.Statement.SetColumn("ID", uuid.New())
	return nil

type User struct {
	Email      string `json:"email"`
	Username   string `json:"username"`

// Organization is the representation of an organization model. It
type Organization struct {
	Name        string    `json:"name"`
	CreatedBy   uuid.UUID `json:"createdBy"`
	Users       []User    `json:"users"    gorm:"many2many:organization_users"`

// OrganizationUsers is a many-to-many join table between Organization and User. It is created explicitely so as to
// help define the foreign key constraints.
type OrganizationUsers struct {
	Organization   Organization
	OrganizationID uuid.UUID `gorm:"primaryKey"`
	User           User
	UserID         uuid.UUID `gorm:"primaryKey"`