Google Code is closing it’s doors simply because nobody is using it. With newer tools such as GitHub and BitBucket, there is no reason for them to continue with the service.

To meet developers where they are, we ourselves migrated nearly a thousand of our own open source projects from Google Code to GitHub. – Chris DiBona

They’re providing a tool for easily migrating your projects to GitHub which is quite nice of them.

Official source:
http://google-opensource.blogspot.ca/2015/03/farewell-to-google-code.html