ClientCredentials.cs

 public static async Task<string> RequestWithClientCredentialsWithPolicy()
{
    async Task<string> GetAccessToken()
    {
        var openIdConnectEndPoint = await DiscoveryClient.GetAsync("http://localhost:5000");
        var tokenClient = new TokenClient(openIdConnectEndPoint.TokenEndpoint, "client1", "123654");
        var accessToken = await tokenClient.RequestClientCredentialsAsync("Api1");

        if (accessToken.IsError)
        {
            Console.WriteLine(accessToken.Error);
            return accessToken.Error;
        }

        Console.WriteLine(accessToken.Json);

        return accessToken.AccessToken;
    }

    using (var client = new HttpClient())
    {
        var accessToken = await GetAccessToken();

        client.SetBearerToken(accessToken);

        var response = await client.GetAsync("http://localhost:5001/api/ApiResourceWithPolicy");

        if (!response.IsSuccessStatusCode)
        {
            return response.StatusCode.ToString();
        }

        var content = await response.Content.ReadAsStringAsync();

        return content;
    }
}