Access a value from setTimeout Observable method

Can you tell me how to access a value from the async setTimeout() observable method? I have written just normal async method as below.But as we all know it doesn't do what I need.How can I use observable here? Any guidance would be really appreciated.

page.ts

loader = this.loadingControllerService.dismissLoaderWhenNoInternet(loader);

provider.ts

 dismissLoaderWhenNoInternet(loader: Loading): Loading {
    setTimeout(() => {
      if (loader) {
        loader = null;
        return loader;//not working here
      }
    }, 5000);
    return loader;
  }