DI Container
Kruda includes a built-in dependency injection container. Services are registered on a *Container and resolved in handlers via *Ctx.
Setting Up
go
c := kruda.NewContainer()
c.Give(&UserService{db: connectDB()})
c.GiveLazy(func() (*DBPool, error) { return connectDB() })
c.GiveNamed("write", &DB{DSN: "primary"})
app := kruda.New(kruda.WithContainer(c))Resolving in Handlers
go
app.Get("/users", func(c *kruda.Ctx) error {
svc := kruda.MustResolve[*UserService](c)
return c.JSON(svc.ListAll())
})Registration Methods
All registration is done on *Container:
| Method | Behavior |
|---|---|
Give(instance) | Singleton — pre-built instance |
GiveLazy(factory) | Lazy singleton — factory runs once on first use |
GiveTransient(factory) | New instance per resolution |
GiveNamed(name, instance) | Named singleton |
GiveAs(instance, ifacePtr) | Register under interface type |
Resolution Functions
In handlers, use package-level generic functions with *Ctx:
| Function | Behavior |
|---|---|
Resolve[T](c) | Returns (T, error) |
MustResolve[T](c) | Returns T, panics on error |
ResolveNamed[T](c, name) | Named resolution with error |
MustResolveNamed[T](c, name) | Named resolution, panics on error |
Modules
Group related services into modules:
go
type UserModule struct{}
func (m *UserModule) Install(c *kruda.Container) error {
c.Give(&UserRepository{})
c.Give(&UserService{})
return nil
}
app.Module(&UserModule{})The Module interface:
go
type Module interface {
Install(c *Container) error
}Dependency Chains
go
c := kruda.NewContainer()
c.Give(&DBPool{dsn: os.Getenv("DATABASE_URL")})
c.Give(&UserRepository{})
c.Give(&UserService{})
app := kruda.New(kruda.WithContainer(c))Example
go
package main
import "github.com/go-kruda/kruda"
type GreetService struct {
prefix string
}
func (s *GreetService) Greet(name string) string {
return s.prefix + " " + name
}
func main() {
c := kruda.NewContainer()
c.Give(&GreetService{prefix: "Hello"})
app := kruda.New(kruda.WithContainer(c))
app.Get("/greet/:name", func(c *kruda.Ctx) error {
svc := kruda.MustResolve[*GreetService](c)
msg := svc.Greet(c.Param("name"))
return c.JSON(map[string]string{"message": msg})
})
app.Listen(":3000")
}See Container API for the full reference.