VB.NET Google drive api v3 for visual studio 2010 and above

Module1.vb

''''''''''''''https://adonetaccess2003.blogspot.com'''''''''''''''''''
Imports Google.Apis.Auth.OAuth2
Imports Google.Apis.Drive.v3
Imports Google.Apis.Drive.v3.Data
Imports Google.Apis.Services
Imports Google.Apis.Util.Store
Imports System.IO
Imports System.Threading
'Save "credentials.json" in your project directory (i.e D:\Google-Drive-example\)
'Refresh 'Solution explorer', show all files, include "credentials.json" into your project
'From "Properties panel" change "Copy to Output Directory" to "Copy Always".
Module Module1
    'If modifying these scopes, delete your previously saved credentials
    'at ~/.credentials/drive-dotnet-quickstart.json
    Dim Scopes() As String = {DriveService.Scope.DriveReadonly}
    Dim ApplicationName As String = "Quickstart"
    Private Service As DriveService = New DriveService
    Public Sub Main()
        Dim credential As UserCredential
        Using Stream = New FileStream("credentials.json", FileMode.Open, FileAccess.Read)
            'The file token.json stores the user's access and refresh tokens, and is created
            'automatically when the authorization flow completes for the first time.
            Dim credPath As String = "token.json"
            credential = GoogleWebAuthorizationBroker.AuthorizeAsync(
                    GoogleClientSecrets.Load(Stream).Secrets,
                    Scopes,
                    "user",
                    CancellationToken.None,
                    New FileDataStore(credPath, True)).Result
            Console.WriteLine("Credential file saved to: " + credPath)

        End Using
        'Create Drive API service.
        Dim Service = New DriveService(New BaseClientService.Initializer() With
            {
                .HttpClientInitializer = credential,
                .ApplicationName = ApplicationName
            })
        ' Define parameters of request.
        Dim listRequest As FilesResource.ListRequest = Service.Files.List()
        listRequest.PageSize = 10
        listRequest.Fields = "nextPageToken, files(id, name)"
        'List files.
        Dim files As IList(Of Data.File) = listRequest.Execute().Files
        Console.WriteLine("Files:")
        If (files IsNot Nothing And files.Count > 0) Then
            For Each file In files
                Console.WriteLine("{0} ({1})", file.Name, file.Id)
            Next
        Else
            Console.WriteLine("No files found.")
        End If
        Console.Read()
    End Sub
End Module

How i can close the service? I mean, how i can get a new conecction everytime if i need the service with other gmail account?