Golangのgormで、PrimaryKeyにXIDを使う ref: http://qiita.com/roothybrid7/items/2db3ccbf46f2bdb9cd00

model.go

// Model is a base model that defines a primary key and timestamp on operation.
type Model struct {
    XID       T.XID          `gorm:"type:varchar(20);primary_key" json:"id"` // XXX: XID on create callback.
    CreatedAt T.ResourceTime `json:"createdAt"`
    UpdatedAt T.ResourceTime `json:"updatedAt"`
}

// SoftModel is a base model to delete a record.
type SoftModel struct {
    XID       T.XID          `gorm:"type:varchar(20);primary_key" json:"id"` // XXX: XID on create callback.
    CreatedAt T.ResourceTime `json:"createdAt"`
    UpdatedAt T.ResourceTime `json:"updatedAt"`
    DeletedAt *time.Time     `json:"deletedAt,omitempty"` // XXX: ポインターだとカラム追加できない
}


// User is a model of user.
type User struct {
    //gorm.Model        // see: https://github.com/jinzhu/gorm#conventions
    SoftModel
    Username       string          `gorm:"size:180;not null;index" json:"username"`
}

repos.go

package repos

import (
    "github.com/jinzhu/gorm"

    T "bitbucket.org/team1/app/module/typedef"
    "bitbucket.org/team1/app/module/util"
)

// Gorm callbacks

func updateXIDWhenCreate(scope *gorm.Scope) {
    if !scope.HasError() {
        scope.SetColumn("XID", *T.NewXID()) // Primary Key
    }
}

func init() {
    // XXX: DBのtimestampをUTCにする
    gorm.NowFunc = util.NowUtcFunc
    gorm.DefaultCallback.Create().Before("gorm:save_before_associations").Register("app:update_xid_when_create", updateXIDWhenCreate)
}

xid.go

package typedef

import (
    "database/sql/driver"
    "errors"

    json "github.com/pquerna/ffjson/ffjson"
    "github.com/rs/xid"
)

// XID redefines a new type to use application.
type XID struct {
    id xid.ID
}

// NewXID creates a new xid.
func NewXID() *XID {
    return &XID{id: xid.New()}
}

// NewXIDFromString creates a XID object to use xid generator.
func NewXIDFromString(str string) *XID {
    id, err := xid.FromString(str)
    if err != nil {
        return nil
    }
    return &XID{id: id}
}

// XIDFromString creates from string representation.
func XIDFromString(str string) (id XID, err error) {
    v, err := xid.FromString(str)
    if err != nil {
        return
    }
    id.id = v
    return
}

// IsZero defines to check whether nil value or not.
func (id XID) IsZero() bool {
    return len(id.id) == 0
}

// EqualString returns both string representation.
func (id XID) EqualString(s string) bool {
    return id.String() == s
}

// String returns xid string representation.
func (id XID) String() string {
    return id.id.String()
}

// Marshalizations

// MarshalJSON returns the encoded JSON string.
func (id XID) MarshalJSON() ([]byte, error) {
    v := id.id
    return []byte(`"` + v.String() + `"`), nil
}

// UnmarshalJSON sets the value that decoded JSON.
func (id *XID) UnmarshalJSON(data []byte) (err error) {
    var v string
    if err = json.Unmarshal(data, &v); err != nil {
        return
    }
    if err = id.Scan(v); err != nil {
        return
    }
    return
}

// Sql driver interface.

// Scan casts a value to xid.ID
// XXX: DBからのvalueは、[]uint8で渡ってくるっぽい(ascii codeが入ってる)
func (id *XID) Scan(value interface{}) (err error) {
    switch v := value.(type) {
    case string:
        id.id, err = xid.FromString(v)
    case []uint8:
        b := make([]byte, len(v))
        for i, a := range v {
            b[i] = byte(a)
        }
        id.id, err = xid.FromString(string(b))
    default:
        err = errors.New("xid.Scan: invalid value")
    }
    return
}

// Value exports the casted object value.
func (id XID) Value() (driver.Value, error) {
    return id.String(), nil
}