I have simple app that get request to website like this:

            using (var httpClient = new HttpClient())
            {
                var response = await httpClient.GetAsync("https://www.microsoft.com");
                Console.WriteLine(response.StatusCode);
            }

This code work fine on Windows, but on Ubuntu 18.04 it crash with error:

System.Net.Http.HttpRequestException: The SSL connection could not be established, see inner exception. ---> System.Security.Authentication.AuthenticationException: The remote certificate is invalid according to the validation procedure.

This code work fine on Ubuntu only with websites that using http protocol.
Why it does not work with https?

dotnet --info:

.NET Core SDK (reflecting any global.json):
Version: 2.1.401
Commit: 91b1c13032

Runtime Environment:
OS Name: ubuntu
OS Version: 18.04
OS Platform: Linux
RID: ubuntu.18.04-x64
Base Path: /usr/share/dotnet/sdk/2.1.401/

Host (useful for support):
Version: 2.1.3
Commit: 124038c13e

.NET Core SDKs installed:
2.1.401 [/usr/share/dotnet/sdk]

.NET Core runtimes installed:
Microsoft.AspNetCore.All 2.1.3 [/usr/share/dotnet/shared/Microsoft.AspNetCore.All]
Microsoft.AspNetCore.App 2.1.3 [/usr/share/dotnet/shared/Microsoft.AspNetCore.App]
Microsoft.NETCore.App 2.1.3 [/usr/share/dotnet/shared/Microsoft.NETCore.App]