Initialize byte array using string [duplicate]

Salsa20 requires a key *[32]byte which I want to provide using a string constant. Passing the key using a type-cast to a slice yield error: argument 4 has incompatible type. I don't know of any way to cast a string (or a slice) as an array.

I don't want to create variable byteKey [32]byte and use copy([:]byteKey, []byte(stringKey)) every time the encryption takes place.

This is my current solution:

func createFeedbackKey() (key [32]byte) {
  const s = "thesingleonegreatairfysecretword"
  copy(key[:], s)
  return
}

var feedbackKey = createFeedbackKey()

That's 6 lines of code with a copy where, imho, a mere typecast should suffice.

Is there a shorter/better way? Something like this maybe?

var key = [...]byte("0123456789ABCDEF0123456789ABCDEF")