github.com/jschaefer-io/godi

Go-DI

Go-DI implements a small and lightweight container used for dependency injection without code generation.

Its main component is the Container interface, which can be instantiated with godi.NewContainer(). Now dependencies can be bound to the container either instantiating or as a singleton and queried from the Container's ResolverFunc.

It's recommended to pass the Container's ResolverFunc with the context of your application, allowing you to access the dependency injection container easily.

// create the container and bind a dependency
container := godi.NewContainer()
container.MustBind("time-service", func(resolver godi.ResolverFunc) any {
    return time.Now()
})

// add resolver to a context
ctx := context.WithValue(context.Background(), "container", container.Resolver())

// use the context to retrieve the resolver and execute it
resolver := ctx.Value("container").(godi.ResolverFunc)
currentTime := godi.MustResolve[time.Time]("time-service", resolver)

fmt.Println(currentTime.Unix())

Types of bound dependencies

Go-DI differentiates two types of dependencies: instantiating and singleton dependencies.

Instantiating Dependencies

Instantiating Dependencies are instantiated every time, they are requested from the dependency container. Every request form the dependency container will therefore yield a new instance.

container.MustBind("rng", func(resolver godi.ResolverFunc) any {
    return rand.Int63()
})
resolver := container.Resolver()

// Will yield different results for all DI requests
fmt.Println(godi.MustResolve[int64]("rng", resolver))
fmt.Println(godi.MustResolve[int64]("rng", resolver))
fmt.Println(godi.MustResolve[int64]("rng", resolver))

Singleton Dependencies

Singleton Dependencies are instantiated only once. All subsequent requests to the dependency container will yield the first and only instantiated instance.

container.MustBindSingleton("rng-once", func(resolver godi.ResolverFunc) any {
    return rand.Int63()
})
resolver := container.Resolver()

// Will yield the same result for all DI requests
fmt.Println(godi.MustResolve[int64]("rng-once", resolver))
fmt.Println(godi.MustResolve[int64]("rng-once", resolver))
fmt.Println(godi.MustResolve[int64]("rng-once", resolver))