Build and run a Dagger pipeline in Go that containerizes an application, runs tests in isolation, and pushes to a registry only if tests pass, using Dagger's native caching

Steps

1. Initialize a Dagger Go module with dagger init --sdk=go --name=ci and scaffold a main.go with a Dagger function that accepts a *dagger.Client context and a source *dagger.Directory parameter
2. In the pipeline function, build a container from the source directory using client.Container().From(baseImage).WithDirectory("/app", source).WithWorkdir("/app").WithExec([]string{"go", "build", "./..."})
3. Run tests in a separate container derived from the build output using .WithExec([]string{"go", "test", "-race", "./..."}); call .Sync(ctx) to execute and return an error if tests fail, preventing the pipeline from continuing
4. Only if Sync returns nil, proceed to push the image to a registry using .Publish(ctx, registryRef) where registryRef includes the digest-addressable tag; capture and return the pushed digest as the function output
5. Use WithMountedCache on the Go module cache directory pointing to a client.CacheVolume("go-modules") so dependency downloads are reused across pipeline runs without manual cache key management
6. Invoke the Dagger pipeline locally with dagger call ci --source=. and in CI with dagger run go run ./ci.go, ensuring the same pipeline code executes identically in both environments