Tutorials: Build a Task Management API

These tutorials teach event sourcing by building a Task Management API from scratch using terraskye/eventsourcing and Gin.

What you'll build

A task management system with:

• Commands: create tasks, assign them, mark as complete
• Queries: list all tasks, personal dashboard
• Real-time projections that update automatically
• Background processing to auto-archive completed tasks

Prerequisites

• Go 1.21+ installed
• Basic understanding of Go structs and interfaces
• Familiarity with HTTP APIs
• No event sourcing knowledge required

Tutorial parts

Part	Topic	What you learn	Time
1	Your first command	Commands, events, event store	30 min
2	Your first query	Queries, live read models	15 min
3	Business rules	State, the decide/evolve pattern	20 min
4	Real-time projections	Event bus, cached projections	25 min
5	Background processing	Processors, sagas	15 min

Total time: ~1.5 hours hands-on

Project structure

Throughout the tutorials you'll build this layout:

task-management/
├── main.go
├── events/
│   ├── task_created.go
│   ├── task_assigned.go
│   └── task_completed.go
├── slices/
│   ├── createtask/
│   │   ├── command.go
│   │   └── http.go
│   ├── completetask/
│   │   ├── command.go
│   │   └── http.go
│   └── listtasks/
│       ├── query.go
│       └── http.go
└── go.mod

This follows Vertical Slice Architecture, where each feature is self-contained.

Initial setup

Create the project:

mkdir task-management && cd task-management
go mod init task-management
go get github.com/terraskye/eventsourcing
go get github.com/terraskye/eventsourcing/eventstore/memory
go get github.com/gin-gonic/gin
go get github.com/google/uuid

Ready? Start with Part 1: Your First Command.