using access token issued from Google & facebook in backend web API - google-oauth

Question

I’m creating a Xamarin mobile app which uses a Resources backend ASP core Restful Web API and an “Identity server 4” for issuing JWT Tokens. And I’m OK with it until now.
Now I want to add social login options to my app. So the user will be able to login with his Google or Facebook account and the app receives a access token. Then the app must send the access token to Resources backend. Then Resources backend checks Access token for validation and returns list of resource items requested by user.
My question is that how the backend Resource should know that the token is issued from google or Facebook to check its validation based on secret and ClientId?
Diagram of what I'm tying to do
If access token is issued from Google {check validity of access token based on OAuth credentials obtained from google}
Else If is issued from Facebook {check validity based on OAuth credentials obtained from Facebook}
Else If is issued from Identity Sever 4 {check validity based on OAuth credentials obtained from Identity Sever 4}.
Is this the solution?
app.UseIdentityServerAuthentication(new IdentityServerAuthenticationOptions
{
Authority = "http://localhost:1941",
RequireHttpsMetadata = false,
EnableCaching = true,
ScopeName = "api1",
ScopeSecret = "secret",
AutomaticAuthenticate = true
});
app.UseGoogleAuthentication(new GoogleOptions
{
ClientId = "[YOUR APP CLIENT ID]",
ClientSecret = "[YOUR APP SECRET]"
});
app.UseFacebookAuthentication(new FacebookOptions
{
ClientId = "[YOUR APP CLIENT ID]",
ClientSecret = "[YOUR APP SECRET]"
});