When we install SharePoint Framework extensions to Visual Studio 2017, and try to create a SharePoint Framework project, it keeps on creating the project and goes into Not Responding mode.
This is related to npm package microsoft/generator-sharepoint version.
The scaffolding procedure has changed in this version and it contains now an additional option to choose which type of client-side component you would like to create (WebPart or Extension in preview). This option was not present in previous versions of microsoft/generator-sharepoint package. The generation in Visual Studio stops at this option.
Upgrade to the version 1.0.4. Download from here.
This will help resolve the issue.