How to connect via client certificate?

I have postgresql cluster from https://cloud.yandex.ru. For connection via psql util, firstly I should download certificate from yandex:

mkdir ~/.postgresql && \
wget "https://storage.yandexcloud.net/cloud-certs/CA.pem" -O ~/.postgresql/root.crt && \
chmod 0600 ~/.postgresql/root.crt

And then I should use the following command:

psql "host=xxx.mdb.yandexcloud.net \
      port=6432 \
      sslmode=verify-full \
      dbname=MY_DATABASE \
      user=MY_USERNAME \
      target_session_attrs=read-write"

I try to connect via npgsql with the following connection string:

Host=rc1a-xxx.mdb.yandexcloud.net;Port=6432;SSL Mode=Require;Trust Server Certificate=true;Database=MY_DATABASE;Username=MY_USERNAME

and it fails with the following error:

info: Microsoft.EntityFrameworkCore.Infrastructure[10403]
      Entity Framework Core 2.2.3-servicing-35854 initialized 'ApplicationContext' using provider 'Npgsql.EntityFrameworkCore.PostgreSQL' with options: None
System.Net.Internals.SocketExceptionFactory+ExtendedSocketException (00000005, 6): No such device or address
   at System.Net.Dns.InternalGetHostByName(String hostName)
   at System.Net.Dns.GetHostAddresses(String hostNameOrAddress)
   at Npgsql.NpgsqlConnector.Connect(NpgsqlTimeout timeout) in C:\projects\npgsql\src\Npgsql\NpgsqlConnector.cs:line 663
   at Npgsql.NpgsqlConnector.RawOpen(NpgsqlTimeout timeout, Boolean async, CancellationToken cancellationToken) in C:\projects\npgsql\src\Npgsql\NpgsqlConnector.cs:line 555
   at Npgsql.NpgsqlConnector.Open(NpgsqlTimeout timeout, Boolean async, CancellationToken cancellationToken) in C:\projects\npgsql\src\Npgsql\NpgsqlConnector.cs:line 414
   at Npgsql.NpgsqlConnection.<>c__DisplayClass32_0.<<Open>g__OpenLong|0>d.MoveNext() in C:\projects\npgsql\src\Npgsql\NpgsqlConnection.cs:line 273
--- End of stack trace from previous location where exception was thrown ---
   at Npgsql.NpgsqlConnection.Open() in C:\projects\npgsql\src\Npgsql\NpgsqlConnection.cs:line 153
   at Npgsql.EntityFrameworkCore.PostgreSQL.Storage.Internal.NpgsqlDatabaseCreator.Exists() in C:\projects\npgsql-entityframeworkcore-postgresql\src\EFCore.PG\Storage\Internal\NpgsqlDatabaseCreator.cs:line 190
   at Microsoft.EntityFrameworkCore.Migrations.HistoryRepository.Exists()
   at Microsoft.EntityFrameworkCore.Migrations.Internal.Migrator.Migrate(String targetMigration)
   at Microsoft.EntityFrameworkCore.Design.Internal.MigrationsOperations.UpdateDatabase(String targetMigration, String contextType)
   at Microsoft.EntityFrameworkCore.Design.OperationExecutor.UpdateDatabase.<>c__DisplayClass0_1.<.ctor>b__0()
   at Microsoft.EntityFrameworkCore.Design.OperationExecutor.OperationBase.Execute(Action action)
No such device or address

My dotnet info:

dotnet --info
.NET Core SDK (reflecting any global.json):
 Version:   2.2.105
 Commit:    7cecb35b92

Runtime Environment:
 OS Name:     ubuntu
 OS Version:  18.04
 OS Platform: Linux
 RID:         ubuntu.18.04-x64
 Base Path:   /usr/share/dotnet/sdk/2.2.105/

Host (useful for support):
  Version: 2.2.3
  Commit:  6b8ad509b6

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

.NET Core runtimes installed:
  Microsoft.AspNetCore.All 2.2.3 [/usr/share/dotnet/shared/Microsoft.AspNetCore.All]
  Microsoft.AspNetCore.App 2.2.3 [/usr/share/dotnet/shared/Microsoft.AspNetCore.App]
  Microsoft.NETCore.App 2.2.3 [/usr/share/dotnet/shared/Microsoft.NETCore.App]

[rusrc]

So I use the yandex cloud too. And was getting error too. Here you are my test connection looks like this.

First install the certificate on my VM mkdir -p ~/.postgresql &&
wget “https://storage.yandexcloud.net/cloud-certs/CA.pem” -O ~/.postgresql/root.crt &&
chmod 0600 ~/.postgresql/root.crt

Then the code example:

public async Task<ActionResult<bool>> CanConnect()
        {
            const string host = "rc4c-blablablablabla.mdb.yandexcloud.net";
            var connection =
                $"Host={host};Port=6432;SSLMode=Require;TrustServerCertificate=true;Database=YOUR_DB_NAME;Username=YOUR_DB_USERNAME;Password=*******";

            var optionsBuilder = new DbContextOptionsBuilder<DbAppContext>();
            optionsBuilder.UseNpgsql(connection, builder =>
            {
                builder.RemoteCertificateValidationCallback((s, c, ch, sslPolicyErrors) =>
                {
                    if (sslPolicyErrors == SslPolicyErrors.None)
                    {
                        return true;
                    }
                    _logService.Error($@"Certificate error: {sslPolicyErrors}, 
                    Do not allow this client to communicate with unauthenticated servers");
                    return false;
                });

                builder.ProvideClientCertificatesCallback(clientCerts =>
                {
                    var clientCertPath = "/home/username/.postgresql/root.crt";
                    // To avoid permission ex run: "sudo chmod -R 777 /home/username/.postgresql/root.crt"
                    var cert = new X509Certificate2(clientCertPath);
                    clientCerts.Add(cert);
                });
            });

            using (var ctx = new DbAppContext(optionsBuilder.Options))
            {
                return await ctx.Database.CanConnectAsync();
            }
        }

[YohDeadfall]

Sorry, fixed the link. The issue is in the main repo.