Getting Started

Estoria requires Go >=1.26.

go get github.com/go-estoria/estoria

The core Estoria components only depend on the Go standard library and github.com/gofrs/uuid/v5 for UUID support. Vendor-specific components are imported separately as needed from estoria-contrib.

Quickstart

Run all of the code below in a Go playground. For complete applications built on Estoria — a collaborative kanban board, an order-fulfillment service, a sensor fleet, chess — see Examples.

Entities

An entity is any type; no interface is required. Provide a factory function that builds one from a UUID:

type User struct {
	ID   uuid.UUID
	Name string
}

func NewUser(id uuid.UUID) User {
	return User{ID: id, Name: "Unknown"}
}

Events

Events must implement estoria.DomainEvent:

type UserNameChanged struct {
	NewName string
}

func (UserNameChanged) EventType() string { return "namechanged" }

func (UserNameChanged) New() estoria.DomainEvent[User] {
	return &UserNameChanged{NewName: "Unknown User"}
}

func (e UserNameChanged) ApplyTo(user User) User {
	user.Name = e.NewName
	return user
}

Aggregates

Create an event store to store events:

eventStore, _ := memory.NewEventStore()

Then, create an aggregate store using the event store, an aggregate type name, your entity factory function, and your event types. The type name becomes part of every aggregate’s stream address, so it must remain stable for the lifetime of your data:

aggregateStore, _ := aggregatestore.New(eventStore, "user", NewUser,
    aggregatestore.WithEventTypes(
        UserNameChanged{},
    ),
)

Now you can begin working with aggregates in your application:

userID := uuid.Must(uuid.NewV4())

// create a new User aggregate
newUser := aggregateStore.New(userID)

// append an event
newUser.Append(UserNameChanged{NewName: "Juliette"})

// save the aggregate
_ = aggregateStore.Save(ctx, newUser, nil)

// load the aggregate
loadedUser, _ := aggregateStore.Load(ctx, userID, nil)

// access the aggregate's state
user := loadedUser.State()

Defining Entities