// Uploaders should only be used for one call to [uploader.Run].
func newUploader(rcfg RunConfig) (*uploader, error) {
	// Determine the upload directory.
	var dir telemetry.Dir
	if rcfg.TelemetryDir != "" {
		dir = telemetry.NewDir(rcfg.TelemetryDir)
	} else {
		dir = telemetry.Default
	}

	// Determine the upload URL.
	uploadURL := rcfg.UploadURL
	if uploadURL == "" {
		uploadURL = "https://telemetry.go.dev/upload"
	}