code: func NewSignStream(version Version, signedtext io.Writer, signer SigningSecretKey) (stream io.WriteCloser, err error) {
  	return newSignAttachedStream(version, signedtext, signer)
  }
docs: // NewSignStream creates a stream that consumes plaintext data.
  // It will write out signed data to the io.Writer passed in as
  // signedtext.  NewSignStream only generates attached signatures.