golang-samber-do

Persona: You are a Go architect setting up dependency injection. You keep the container at the composition root, depend on interfaces not concrete types, and treat provider errors as first-class failures.

Using samber/do for Dependency Injection in Go

Type-safe dependency injection toolkit for Go based on Go 1.18+ generics.

Official Resources:

• pkg.go.dev/github.com/samber/do/v2
• do.samber.dev
• github.com/samber/do/v2

This skill is not exhaustive — refer to library documentation and code examples for more information:

• For Go package docs, symbols, versions, importers, and known vulnerabilities, → See samber/cc-skills-golang@golang-pkg-go-dev skill (godig), preferred over Context7 for Go package facts.
• To navigate this library's usage in your own code (definitions, call sites, diagnostics), → See samber/cc-skills-golang@golang-gopls skill (gopls).
• Context7 remains a fallback for docs not indexed on pkg.go.dev.

Install v2 — v1 is superseded and lacks the generics-based container, scopes, and lifecycle hooks documented below, so v1-era guidance misleads on every API in this skill:

go get -u github.com/samber/do/v2

Core Concepts

The Injector (Container)

import "github.com/samber/do/v2"

injector := do.New()

Service Types

• Lazy (default): Created when first requested
• Eager: Created immediately when the container starts
• Transient: New instance created on every request
• Value: Pre-created value, no instantiation

Provider Functions

Services MUST be registered via provider functions:

type Provider[T any] func(i Injector) (T, error)

Basic Usage

1. Define and Register Services

Follow "Accept Interfaces, Return Structs":

// Register a service (lazy by default)
do.Provide(injector, func(i do.Injector) (Database, error) {
    return &PostgreSQLDatabase{connString: "postgres://..."}, nil
})

// Register a pre-created value
do.ProvideValue(injector, &Config{Port: 8080})

// Register a transient service (new instance each time)
do.ProvideTransient(injector, func(i do.Injector) (*Logger, error) {
    return &Logger{}, nil
})

// Register an eager service (created immediately at startup)
do.ProvideValue(injector, &Config{Port: 8080})