golang-uber-dig

Embed dig.In in a parameter struct and pass it as the constructor's single argument. Each field becomes a dependency the container fills automatically, and adding a new dependency is a one-line change instead of a signature break.

Use dig.Name("primary") and dig.Name("readonly") as Provide options, or name tags on a dig.Out result struct. Consumers then add name:"primary" or name:"readonly" tags to dig.In fields to receive the right instance.

fx is built on dig and shares the same container engine and DI primitives. fx adds lifecycle hooks, a module system, signal-aware Run, and startup timeouts, while dig provides only the wiring graph for apps managing their own lifecycle.

Create the container with dig.New(dig.DryRun(true)), register the same providers as production, and call Invoke on the composition root. dig validates types structurally without executing constructors, catching missing providers in CI.

No. The container belongs only at the composition root in main. Inject typed dependencies as constructor parameters instead, since passing the container creates a service-locator anti-pattern that hides dependencies and breaks testability.

Tag each handler's dig.Out field with group:"routes" and consume a []Handler field tagged with the same group in dig.In. Group order is not guaranteed, so provide an explicit ordered slice from one constructor when ordering matters.