CORS net/http middleware

go-chi/cors is a fork of github.com/rs/cors that provides a net/http compatible middleware for performing preflight CORS checks on the server side. These headers are required for using the browser native Fetch API.

This middleware is designed to be used as a top-level middleware on the chi router. Applying with within a r.Group() or using With() will not work without routes matching OPTIONS added.

Usage

func main() {
  r := chi.NewRouter()

  // Basic CORS
  // for more ideas, see: https://developer.github.com/v3/#cross-origin-resource-sharing
  r.Use(cors.Handler(cors.Options{
    // AllowedOrigins:   []string{"https://foo.com"}, // Use this to allow specific origin hosts
    AllowedOrigins:   []string{"https://*", "http://*"},
    // AllowOriginFunc:  func(r *http.Request, origin string) bool { return true },
    AllowedMethods:   []string{"GET", "POST", "PUT", "DELETE", "OPTIONS"},
    AllowedHeaders:   []string{"Accept", "Authorization", "Content-Type", "X-CSRF-Token"},
    ExposedHeaders:   []string{"Link"},
    AllowCredentials: false,
    MaxAge:           300, // Maximum value not ignored by any of major browsers
  }))

  r.Get("/", func(w http.ResponseWriter, r *http.Request) {
    w.Write([]byte("welcome"))
  })

  http.ListenAndServe(":3000", r)
}

Credits

All credit for the original work of this middleware goes out to github.com/rs.