accessing google drive with a service account and C#

GoogleDriveServiceAccountcsharp

string[] scopes = new string[] {DriveService.Scope.Drive}; // Full access

var keyFilePath = @"c:\file.p12" ;    // Downloaded from https://console.developers.google.com
var serviceAccountEmail = "xx@developer.gserviceaccount.com";  // found https://console.developers.google.com

//loading the Key file
var certificate = new X509Certificate2(keyFilePath, "notasecret", X509KeyStorageFlags.Exportable);
var credential = new ServiceAccountCredential( new ServiceAccountCredential.Initializer(serviceAccountEmail) {
                                                   Scopes = scopes}.FromCertificate(certificate));

Can you please help with JSON key, instead of p12