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. 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": // 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) do . Provide ( injector , do . Eager ( & Config { Port : 8080 } ) ) 2. Invoke Services The container MUST only be accessed at the composition root: // Invoke with error handling db , err := do . Invoke [ Database ] ( injector ) // MustInvoke panics on error (use when confident service exists) 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: // Register concrete type do . Provide ( injector , func ( i do . Injector ) ( * PostgreSQLDatabase , error ) { return & PostgreSQLDatabase { } , nil } ) // Invoke directly as interface (implicit aliasing) 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: // infrastructure/package.go 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 } ) , ) // main.go 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.ProvideT Register lazy service (default) do.ProvideNamedT Register named lazy service do.ProvideValueT Register pre-created value do.ProvideNamedValueT Register named value do.ProvideTransientT Register new instance each time do.ProvideNamedTransientT Register named transient service do.Package() Group service registrations Invocation Function Purpose do.InvokeT Get service (with error) do.InvokeNamedT Get named service do.InvokeAsT Get first service matching interface do.InvokeStructT Inject into struct fields using tags do.MustInvokeT Get service (panic on error) do.MustInvokeNamedT Get named service (panic on error) do.MustInvokeAsT Get service by interface (panic on error) do.MustInvokeStructT 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