I'm still on Go 1.0.2. However, I strongly doubt that having 1.1 yields the correct result in the amount of time that the article boasts; I rewrote the program in C (direct translation), and with both clang and gcc, I get timings of around 2m05s. It's hard to believe that for a CPU-bound task, a Go program would be 200x faster than a C program.

That is not quite right, before 1.1 int was 32-bit on all platforms and post 1.1 an int is 32-bit on 32-bit platforms and 64-bit on 64-bit platforms.

You are supposed to use int when you don't care about its size (int = native word size). If you are writing a program where it matters you should explicitly use int32 or int64.