Static Assets

ko can also bundle static assets into the images it produces.

By convention, any contents of a directory named <importpath>/kodata/ will be bundled into the image, and the path where it's available in the image will be identified by the environment variable KO_DATA_PATH.

As an example, you can bundle and serve static contents in your image:

cmd/
  app/
    main.go
    kodata/
      favicon.ico
      index.html

Then, in your main.go:

func main() {
    http.Handle("/", http.FileServer(http.Dir(os.Getenv("KO_DATA_PATH"))))
    log.Fatal(http.ListenAndServe(":8080", nil))
}

You can simulate ko's behavior outside of the container image by setting the KO_DATA_PATH environment variable yourself with KO_DATA_PATH=cmd/app/kodata/ go run ./cmd/app.

💡 Tip: Symlinks in kodata are followed and included as well. For example, you can include Git commit information in your image with ln -s -r .git/HEAD ./cmd/app/kodata/

Also note that http.FileServer will not serve the Last-Modified header (or validate If-Modified-Since request headers) because ko does not embed timestamps by default.

This can be supported by manually setting the KO_DATA_DATE_EPOCH environment variable during build (See FAQ).