Tried that too, was not working.
But ive got it now, it is  step2 := base58.Decode(step1) and u have to include  "github.com/conformal/btcutil/base58" instead.

Next problem: the wire-package was moved to the the btcd package, so
step5 := btcwire.DoubleSha256(step3)
fmt.Printf("4/5 - Double SHA-256 hash of 3: %x\n", step5)

isnt working anymore. Im looking for the DoubleSha256 func in the btcd/wire dictionary, but i cant find it...