[LVB]

You're correct, but in the interest of:

We’ll discuss these topics only briefly here, pushing most details off to later chapters, since the primary goal right now is to give you an idea of what Go looks like...

it's probably clearer to use the default random source.

[rmcpherson]

Good point, but I also think it will be confusing to beginners who compile and run the program only to find that it always generates the same figure without any explanation as to why. Both the package documentation and text say that the generated figures will be random.

The fix is just a couple lines and, I would argue, should be included in the source to eliminate the surprising behavior. http://play.golang.org/p/1WlhOdJ1pk