Redirect URI with Google using asp.net MVC

I am too lazy to write a properly formatted answer, I placed these comments in code for myself to remember how to resolve this issue. It is not really an issue, just something I never bothered to read properly :) But this is what you can do to make it work. There 2 options how you can do it. I have tried both and both options work just fine. I went with the first one for now, it really doesnt matter. Here are my comments in Startup.Auth.cs file.

// My notes to resolve Google Error: redirect_uri_mismatch error
// By default GoogleOAuth2AuthenticationOptions has CallbackPath defined as "/signin-google"
// https://msdn.microsoft.com/en-us/library/microsoft.owin.security.google.googleoauth2authenticationoptions(v=vs.113).aspx
// But the real path should be Controller/Action: for this application it is "/Account/ExternalLoginCallback"

// There are 2 ways to define it properly:
// 1) Add a new route in RouteConfig.cs that will map "/signin-google" into "/Account/ExternalLoginCallback":
// routes.MapRoute(name: "signin-google", url: "signin-google", defaults: new { controller = "Account", action = "ExternalLoginCallback" });
// Remember, in Google Developers Console you must have your "/signin-google" redirect URI, since that is what your app sends to Google

// 2) Completely overwrite built-in "/signin-google" path.
// Owerwrite CallbackPath right here by adding this line after ClientSecret:
// CallbackPath = new PathString("/Account/ExternalLoginCallback")
// Remember, in Google Developers Console you must have "/Account/ExternalLoginCallback" redirect URI, since now that is what your app sends to Google

app.UseGoogleAuthentication(new GoogleOAuth2AuthenticationOptions()
{
    ClientId = "xxxxxxxxxxxxxxxxxxxx",
    ClientSecret = "xxxxxxxxxxxxxxxxxxxxxxxx"
});