code: func Handler(handler http.Handler) http.Handler {
  	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
  		checks := CheckStatus()
  		if len(checks) != 0 {
  			errcode.ServeJSON(w, errcode.ErrorCodeUnavailable.
  				WithDetail("health check failed: please see /debug/health"))
  			return
  		}
  
  		handler.ServeHTTP(w, r) // pass through
  	})
  }
docs: // Handler returns a handler that will return 503 response code if the health
  // checks have failed. If everything is okay with the health checks, the
  // handler will pass through to the provided handler. Use this handler to
  // disable a web application when the health checks fail.