Skill: samber/golang-samber-do (version 1.2.1)

--- name: golang-samber-do description: "Dependency injection in Golang using samber/do — service containers, lifecycle management, scopes, health checks, graceful shutdown, and module organization. Apply when using or adopting samber/do, when the codebase imports github.com/samber/do or github.com/samber/do/v2, or when refactoring manual constructor injection into a DI container." user-invocable: true license: MIT compatibility: Designed for Claude Code or similar AI coding agents, and for projects using Golang. metadata: author: samber version: "1.2.1" openclaw: emoji: "💉" homepage: https://github.com/samber/cc-skills-golang requires: bins: - go install: [] skill-library-version: "2.0.0" allowed-tools: Read Edit Write Glob Grep Bash(go:*) Bash(golangci-lint:*) Bash(git:*) Agent WebFetch mcp__context7__resolve-library-id mcp__context7__query-docs --- **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](https://pkg.go.dev/github.com/samber/do/v2) - [do.samber.dev](https://do.samber.dev) - [github.com/samber/do/v2](https://github.com/samber/do) 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: ```bash go get -u github.com/samber/do/v2 ``` ## Core Concepts ### The Injector (Container) ```go 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: ```go type Provider[T any] func(i Injector) (T, error) ``` ## Basic Usage ### 1. Define and Register Services Follow "Accept Interfaces, Return Structs": ```go // 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}) ``` ### 2. Invoke Services The container MUST only be accessed at the composition root: ```go // 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 ```go 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: ```go // 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: ```go 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: ```go // 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 ```go 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 1. Depend on interfaces, not concrete types — lets you swap implementations in tests without touching production code 2. Each service should have one job — services with multiple responsibilities are harder to test and harder to replace 3. Keep dependency trees shallow — chains beyond 3-4 levels make initialization order fragile and errors harder to trace 4. Handle errors in provider functions — a silently failing provider creates a broken service that crashes later in unexpected places 5. 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](./references/advanced.md). For testing patterns (cloning, overrides, mocks), see [Testing](./references/testing.md). ## 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


Security scan verdicts — ClawScan: clean | static analysis: clean | VirusTotal: clean | SkillSpector: clean (LOW)