Go: Are there any fun programming assignments/exercises one might do to learn Go?

[Igor Mechnikov]

I took a look at Go Tour.
Are there any exercises, perhaps with walk through solutions, that are a step above 'Hello World'?
Maybe a simple word game, math puzzle ala Project Euler, all written in idiomatic Go.

[Mark Summerfield]

Hi Igor,

Yes, my book provides graded exercises and has solutions. The book's entire source code is available from Programming in Go.