I've got a little Swift Language "search engine" that I built with Go on App Engine. I haven't crawled any sites (yet). I simply created a Go data structure to do in memory searches because I didn't feel like using Google's data store.

Here's the site: http://www.h4labs.com/dev/ios/swift.html

Here's the data: https://github.com/melling/SwiftResources/blob/master/swift_...

I'm approaching 1400 URL's and it's still snappy. I was hoping Go's claimed "efficiency" would keep freely hosted a bit longer than Python.