Timeout connecting SQL Server during the post-login phase

I'm getting this error:

Microsoft.Data.SqlClient.SqlException (0x80131904): Connection Timeout Expired.  The timeout period elapsed during the post-login phase.  The connection could have timed out while waiting for server to complete the login process and respond; Or it could have timed out while attempting to create multiple active connections.  The duration spent while attempting to connect to this server was - [Pre-Login] initialization=33; handshake=152; [Login] initialization=2; authentication=8; [Post-Login] complete=30553;
 ---> System.ComponentModel.Win32Exception (258): Unknown error 258
   at Microsoft.Data.SqlClient.SqlInternalConnection.OnError(SqlException exception, Boolean breakConnection, Action`1 wrapCloseInAction)
   at Microsoft.Data.SqlClient.TdsParser.ThrowExceptionAndWarning(TdsParserStateObject stateObj, Boolean callerHasConnectionLock, Boolean asyncClose)
   at Microsoft.Data.SqlClient.TdsParserStateObject.ThrowExceptionAndWarning(Boolean callerHasConnectionLock, Boolean asyncClose)
   at Microsoft.Data.SqlClient.TdsParserStateObject.ReadSniError(TdsParserStateObject stateObj, UInt32 error)
   at Microsoft.Data.SqlClient.TdsParserStateObject.ReadSniSyncOverAsync()
   at Microsoft.Data.SqlClient.TdsParserStateObject.TryReadNetworkPacket()
   at Microsoft.Data.SqlClient.TdsParserStateObject.TryPrepareBuffer()
   at Microsoft.Data.SqlClient.TdsParserStateObject.TryReadByte(Byte& value)
   at Microsoft.Data.SqlClient.TdsParser.TryRun(RunBehavior runBehavior, SqlCommand cmdHandler, SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, TdsParserStateObject stateObj, Boolean& dataReady)
   at Microsoft.Data.SqlClient.TdsParser.Run(RunBehavior runBehavior, SqlCommand cmdHandler, SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, TdsParserStateObject stateObj)
   at Microsoft.Data.SqlClient.SqlInternalConnectionTds.CompleteLogin(Boolean enlistOK)
   at Microsoft.Data.SqlClient.SqlInternalConnectionTds.AttemptOneLogin(ServerInfo serverInfo, String newPassword, SecureString newSecurePassword, Boolean ignoreSniOpenTimeout, TimeoutTimer timeout, Boolean withFailover)
   at Microsoft.Data.SqlClient.SqlInternalConnectionTds.LoginNoFailover(ServerInfo serverInfo, String newPassword, SecureString newSecurePassword, Boolean redirectedUserInstance, SqlConnectionString connectionOptions, SqlCredential credential, TimeoutTimer timeout)
   at Microsoft.Data.SqlClient.SqlInternalConnectionTds.OpenLoginEnlist(TimeoutTimer timeout, SqlConnectionString connectionOptions, SqlCredential credential, String newPassword, SecureString newSecurePassword, Boolean redirectedUserInstance)
   at Microsoft.Data.SqlClient.SqlInternalConnectionTds..ctor(DbConnectionPoolIdentity identity, SqlConnectionString connectionOptions, SqlCredential credential, Object providerInfo, String newPassword, SecureString newSecurePassword, Boolean redirectedUserInstance, SqlConnectionString userConnectionOptions, SessionData reconnectSessionData, Boolean applyTransientFaultHandling, String accessToken, DbConnectionPool pool, SqlAuthenticationProviderManager sqlAuthProviderManager)
   at Microsoft.Data.SqlClient.SqlConnectionFactory.CreateConnection(DbConnectionOptions options, DbConnectionPoolKey poolKey, Object poolGroupProviderInfo, DbConnectionPool pool, DbConnection owningConnection, DbConnectionOptions userOptions)
   at Microsoft.Data.ProviderBase.DbConnectionFactory.CreatePooledConnection(DbConnectionPool pool, DbConnection owningObject, DbConnectionOptions options, DbConnectionPoolKey poolKey, DbConnectionOptions userOptions)
   at Microsoft.Data.ProviderBase.DbConnectionPool.CreateObject(DbConnection owningObject, DbConnectionOptions userOptions, DbConnectionInternal oldConnection)
   at Microsoft.Data.ProviderBase.DbConnectionPool.UserCreateRequest(DbConnection owningObject, DbConnectionOptions userOptions, DbConnectionInternal oldConnection)
   at Microsoft.Data.ProviderBase.DbConnectionPool.TryGetConnection(DbConnection owningObject, UInt32 waitForMultipleObjectsTimeout, Boolean allowCreate, Boolean onlyOneCheckConnection, DbConnectionOptions userOptions, DbConnectionInternal& connection)
   at Microsoft.Data.ProviderBase.DbConnectionPool.TryGetConnection(DbConnection owningObject, TaskCompletionSource`1 retry, DbConnectionOptions userOptions, DbConnectionInternal& connection)
   at Microsoft.Data.ProviderBase.DbConnectionFactory.TryGetConnection(DbConnection owningConnection, TaskCompletionSource`1 retry, DbConnectionOptions userOptions, DbConnectionInternal oldConnection, DbConnectionInternal& connection)
   at Microsoft.Data.ProviderBase.DbConnectionInternal.TryOpenConnectionInternal(DbConnection outerConnection, DbConnectionFactory connectionFactory, TaskCompletionSource`1 retry, DbConnectionOptions userOptions)
   at Microsoft.Data.ProviderBase.DbConnectionClosed.TryOpenConnection(DbConnection outerConnection, DbConnectionFactory connectionFactory, TaskCompletionSource`1 retry, DbConnectionOptions userOptions)
   at Microsoft.Data.SqlClient.SqlConnection.TryOpen(TaskCompletionSource`1 retry)
   at Microsoft.Data.SqlClient.SqlConnection.Open()
   at OctubreWebService.Features.NumericSamples.NumericSampleService.GetNumericSamples(NumericSampleRequest input) in /source/OctubreWebService/Features/NumericSamples/NumericSampleService.cs:line 48
   at OctubreWebService.Features.NumericSamples.NumericSampleService.GetNumericSamples(NumericSampleRequest input) in /source/OctubreWebService/Features/NumericSamples/NumericSampleService.cs:line 52
   at OctubreWebService.Features.NumericSamples.NumericSampleController.GetNumericSamples(String apiKey, NumericSampleRequest input) in /source/OctubreWebService/Features/NumericSamples/NumericSampleController.cs:line 97
   at lambda_method(Closure , Object )
   at Microsoft.Extensions.Internal.ObjectMethodExecutorAwaitable.Awaiter.GetResult()
   at Microsoft.AspNetCore.Mvc.Infrastructure.ActionMethodExecutor.AwaitableObjectResultExecutor.Execute(IActionResultTypeMapper mapper, ObjectMethodExecutor executor, Object controller, Object[] arguments)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.<InvokeActionMethodAsync>g__Awaited|12_0(ControllerActionInvoker invoker, ValueTask`1 actionResultValueTask)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.<InvokeNextActionFilterAsync>g__Awaited|10_0(ControllerActionInvoker invoker, Task lastTask, State next, Scope scope, Object state, Boolean isCompleted)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.Rethrow(ActionExecutedContextSealed context)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.Next(State& next, Scope& scope, Object& state, Boolean& isCompleted)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.InvokeInnerFilterAsync()

When try to connect to a Sql Server with this connection string:

Server=mysqlserver,1433;Initial Catalog=Octubre;Persist Security Info=False;User ID=myuser;Password=xxxx;MultipleActiveResultSets=False;Encrypt=True;TrustServerCertificate=True;Connection Timeout=30;

I'm using Microsoft.Data.SqlClient package and the code is simple:

var sql = ...; // removed for simplicty

_logger.LogDebug("Connecting using: " + _settings.OctubreConnectionString);

await using var conn = new SqlConnection(_settings.OctubreConnectionString); // Error throws in this line

conn.Open();

_logger.LogDebug($"Connection state: {conn.State}");

_logger.LogDebug($"Running query {sql}");

return new NumericSampleResponse
{
    List = await conn.QueryAsync<NumericSampleResponse.NumericSampleResponseDto>(sql, 
        new { input.From, input.To, input.TagNames, FromRow = input.FromRow + 1, ToRow = input.FromRow + input.RowCount }
            )
};

The application work fine in the development machine, the error is getting when I try launch that from docker container.

Docker host machine is running on a Ubuntu 18.04 Linux. I have tried to connect to the database using mssql tools docker image (https://hub.docker.com/_/microsoft-mssql-tools) and works fine, I can connect and run some queries using sqlcmd.

I have tried changing connection string trusting and not trust in server certificates, encrypt true and false, with and without tcp ...

I have tried using System.Data.SqlClient, the same error.

I thought it was a problem with communication between linux and sql server, due to sql server is in a windows domain and linux is outside, but I have tried to connect with other database server in windows domain and it works fine.

Any ideas?

UPDATE

SQL Server Version: 9.00.3077.00 (SQL Server 2005, I can't upgrade it)
.Net Core version: 3.1

Dockerfile:

# https://hub.docker.com/_/microsoft-dotnet-core
FROM mcr.microsoft.com/dotnet/core/sdk:3.1 AS build
WORKDIR /source

# copy csproj and restore as distinct layers
COPY *.sln .
COPY OctubreWebService/*.csproj ./OctubreWebService/
RUN dotnet restore -r linux-x64

# copy everything else and build app
COPY OctubreWebService/. ./OctubreWebService/
WORKDIR /source/OctubreWebService
RUN dotnet publish -c release -o /app -r linux-x64 --self-contained false --no-restore

# final stage/image
FROM mcr.microsoft.com/dotnet/core/aspnet:3.1-bionic
WORKDIR /app
COPY --from=build /app ./
ENTRYPOINT ["./OctubreWebService"]

The Minimum supported version of System.Data.SqlClient is SqlServer 2008 R2 SP3.I'm sorry for you.