Getting problem in msgbox

Public Class Form1

    Private Sub Button1_Click(sender As System.Object, e As System.EventArgs) Handles Button1.Click
        Try
            'do some work
            'for instance I'm intentionally creating an exception
            Throw New Exception("test error message")
        Catch ex As Exception
            Dim t As New Threading.Thread(New Threading.ParameterizedThreadStart(AddressOf shoMsg))
            t.Start(ex)
        End Try
        
    End Sub

    Private Sub shoMsg(ex As Exception)
        MessageBox.Show(ex.Message)
    End Sub
End Class