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:
This skill is not exhaustive. Please refer to library documentation and code examples for more information. Context7 can help as a discoverability platform.
DO NOT USE v1 OF THIS LIBRARY. INSTALL v2 INSTEAD:
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":
do.Provide(injector, func(i do.Injector) (Database, error) {
return &PostgreSQLDatabase{connString: "postgres://..."}, nil
})
do.ProvideValue(injector, &Config{Port: 8080})
do.ProvideTransient(injector, func(i do.Injector) (*Logger, error) {
return &Logger{}, nil
})
do.Provide(injector, do.Eager(&Config{Port: 8080}))
2. Invoke Services
The container MUST only be accessed at the composition root:
db, err := do.Invoke[Database](injector)
db := do.MustInvoke[Database](injector)
3. Service Dependencies
func NewUserService(i do.Injector) (UserService, error) {
db := do.MustInvoke[Database](i)
cache := do.MustInvoke[Cache](i)
return &userService{db: db, cache: cache}, nil
}
do.Provide(injector, NewUserService)
4. Implicit Aliasing (Preferred)
Register a concrete type and invoke as an interface without explicit aliasing:
do.Provide(injector, func(i do.Injector) (*PostgreSQLDatabase, error) {
return &PostgreSQLDatabase{}, nil
})
db := do.MustInvokeAs[Database](injector)
5. Named Services
Register multiple services of the same type:
do.ProvideNamed(injector, "primary-db", func(i do.Injector) (*Database, error) {
return &Database{URL: "postgres://primary..."}, nil
})
mainDB := do.MustInvokeNamed[*Database](injector, "primary-db")
Package Organization
Use do.Package() to organize service registration by module:
var Package = do.Package(
do.Lazy(func(i do.Injector) (*postgres.DB, error) {
cfg := do.MustInvoke[*Config](i)
return postgres.Connect(cfg.DatabaseURL)
}),
do.Lazy(func(i do.Injector) (*redis.Client, error) {
cfg := do.MustInvoke[*Config](i)
return redis.NewClient(cfg.RedisURL), nil
}),
)
injector := do.New(infrastructure.Package, service.Package)
Full Application Setup
func main() {
injector := do.New(
infrastructure.Package,
repository.Package,
service.Package,
transport.Package,
)
server := do.MustInvoke[*http.Server](injector)
go server.ListenAndServe()
_ = injector.ShutdownOnSignalsWithContext(context.Background(), os.Interrupt)
}
Best Practices
- Depend on interfaces, not concrete types — lets you swap implementations in tests without touching production code
- Each service should have one job — services with multiple responsibilities are harder to test and harder to replace
- Keep dependency trees shallow — chains beyond 3-4 levels make initialization order fragile and errors harder to trace
- Handle errors in provider functions — a silently failing provider creates a broken service that crashes later in unexpected places
- Use scopes to organize services by lifecycle — request-scoped services prevent leaks, global services prevent redundant initialization
For scopes, lifecycle management, struct injection, and debugging, see Advanced Usage.
For testing patterns (cloning, overrides, mocks), see Testing.
Quick Reference
Registration
| Function |
Purpose |
do.Provide[T]() |
Register lazy service (default) |
do.ProvideNamed[T]() |
Register named lazy service |
do.ProvideValue[T]() |
Register pre-created value |
do.ProvideNamedValue[T]() |
Register named value |
do.ProvideTransient[T]() |
Register new instance each time |
do.ProvideNamedTransient[T]() |
Register named transient service |
do.Package() |
Group service registrations |
Invocation
| Function |
Purpose |
do.Invoke[T]() |
Get service (with error) |
do.InvokeNamed[T]() |
Get named service |
do.InvokeAs[T]() |
Get first service matching interface |
do.InvokeStruct[T]() |
Inject into struct fields using tags |
do.MustInvoke[T]() |
Get service (panic on error) |
do.MustInvokeNamed[T]() |
Get named service (panic on error) |
do.MustInvokeAs[T]() |
Get service by interface (panic on error) |
do.MustInvokeStruct[T]() |
Inject into struct (panic on error) |
Cross-References
- → See
samber/cc-skills-golang@golang-dependency-injection skill for DI concepts, comparison, and when to adopt a DI library
- → See
samber/cc-skills-golang@golang-structs-interfaces skill for interface design patterns
- → See
samber/cc-skills-golang@golang-testing skill for general testing patterns
