A modern, type-safe dependency injection framework for Go 1.25+.

• Type-safe generics - Compile-time type checking with Provide[T] and Invoke[T]
• Auto-wiring - Constructor injection and struct tag injection
• Hot reload - Replace services at runtime without restart
• Zero dependencies - Only Go standard library
• Cycle detection - Automatically detects circular dependencies
• Multiple scopes - Singleton, Transient, Request, Pooled
• Lifecycle management - OnStart/OnStop hooks with ordering
• Lazy providers - Defer instantiation until first use
• Parallel startup - Start independent services concurrently
• Modules - Group related providers
• Interface binding - Bind interfaces to implementations
• Decorators - Wrap services with cross-cutting concerns
• Health checks - Liveness and readiness probes
• Optional dependencies - Type-safe optional resolution

go get github.com/danpasecinic/needle

c := needle.New()

needle.ProvideValue(c, &Config{Port: 8080})
needle.Provide(c, func(ctx context.Context, r needle.Resolver) (*Server, error) {
    return &Server{Config: needle.MustInvoke[*Config](c)}, nil
})

server := needle.MustInvoke[*Server](c)

See the examples directory:

• basic - Simple dependency chain
• autowire - Struct-based injection
• httpserver - HTTP server with lifecycle
• modules - Modules and interface binding
• scopes - Singleton, Transient, Request, Pooled
• decorators - Cross-cutting concerns
• lazy - Deferred instantiation
• healthchecks - Liveness and readiness probes
• optional - Optional dependencies with fallbacks
• parallel - Parallel startup/shutdown

Needle wins benchmark categories against uber/fx, samber/do, and uber/dig.

Needle is 50x faster than Fx for provider registration.

*Fx resolves at startup, not on-demand.

When services have initialization work (database connections, HTTP clients, etc.):

Run benchmarks: cd benchmark && make run

See pkg.go.dev for full API documentation.

MIT License - see LICENSE for details.