
@vishalpatel14 not a magento issue but your environments.
The cli PHP under windows is 5.6 but Wampserver is running php 7 .. Run composer update with
--ignore-platform-reqs or run composer with the right php in the cli also.
@FinBoWa
Thank you for the quick support. Issue was my CLI version and its resolved now. You can close the ticket,
After completion of update still its showing same version 2.1.9 not the 2.2.0. Please have a look.
@vishalpatel14 please refer to the Community Forums or the Magento Stack Exchange site for advice or general discussion about this issue. The GitHub issue tracker is intended for Magento Core technical issues only.
Your problem seems to be related to the platform you are using.
After Solving my environment problem this new error have came. Please have a look.

Most helpful comment
@vishalpatel14 not a magento issue but your environments.
The cli PHP under windows is 5.6 but Wampserver is running php 7 .. Run composer update with
--ignore-platform-reqsor run composer with the right php in the cli also.