go-dependency-injection

Pass dependencies through constructors that accept interfaces and return structs, then wire everything in main() at the composition root. For small projects under 10 services, manual constructor injection is sufficient without any library.

Wire generates code at compile time with no reflection but requires a build step. Fx uses reflection with built-in lifecycle hooks and modules. Samber/do uses generics for compile-time safety with lazy loading, health checks, and container cloning.

Stay manual below 10 services. Consider a library at 10-20 services with cross-cutting concerns, and strongly adopt one past 20 services or when you need health checks, graceful shutdown, lazy loading, or scopes.

No. Wire creates all dependencies eagerly and has no built-in lifecycle management, health checks, or graceful shutdown. It generates plain Go constructor calls, so lifecycle handling must be written manually.

Passing the container turns it into a service locator, hiding each component's real dependencies. Inject only the specific dependencies each service needs through its constructor so requirements stay explicit and testable.

Inventory every global and init()-created dependency, define interfaces at consumption points, then convert services to constructor injection incrementally. Move all wiring into main() and verify each service builds in tests with mocks.