'The session is not open' in ListDirectoryAsync

从 SftpClient.ListDirectoryAsync 开始，通过 SftpSession.GetCanonicalPathAsync 和 SftpSession.SendRequest 跟踪报告的路径。尝试使用相同凭据的多个 SftpClient 实例，在列出不同文件夹时复现该故障，并检查 ConnectAsync、ListDirectoryAsync 和 Disconnect 周围的会话生命周期。只有在理解了罕见的 'The session is not open' 故障，并通过可靠的测试或记录在案的限制加以覆盖后，才算完成。

On rare occasions, I see 'The session is not open' in ListDirectoryAsync.
The last time I saw it, it was for a server where multiple instances of sftpClient might get created simultaneously with the same username/password, but working with different folders.

SSH.NET 2025.1.0 .Net 9.

My code looks like this:

try
{
    await sftpClient.ConnectAsync(cancellationToken);
	
    await sftpClient.ChangeDirectoryAsync(path, cancellationToken);
    var asyncList = sftpClient.ListDirectoryAsync(path, cancellationToken);
}
finally
{
	if (sftpClient.IsConnected)
		sftpClient.Disconnect();
}

"Type": "System.InvalidOperationException",
"HResult": -2146233079,
"Message": "The session is not open.",
"Source": "Renci.SshNet",
"StackTrace": " at Renci.SshNet.Sftp.SftpSession.SendRequest(SftpRequest request)\r\n at Renci.SshNet.Sftp.SftpSession.GetCanonicalPathAsync(String path, CancellationToken cancellationToken)\r\n at Renci.SshNet.SftpClient.ListDirectoryAsync(String path, CancellationToken cancellationToken)+MoveNext()\r\n at Renci.SshNet.SftpClient.ListDirectoryAsync(String path, CancellationToken cancellationToken)+System.Threading.Tasks.Sources.IValueTaskSource.GetResult()",
"TargetSite": "Void SendRequest(Renci.SshNet.Sftp.Requests.SftpRequest)"