code: func gogpgme_seekfunc(handle unsafe.Pointer, offset C.gpgme_off_t, whence C.int) C.gpgme_off_t {
  	d := callbackLookup(uintptr(handle)).(*Data)
  	n, err := d.s.Seek(int64(offset), int(whence))
  	if err != nil {
  		C.gpgme_err_set_errno(C.EIO)
  		return -1
  	}
  	return C.gpgme_off_t(n)
  }
docs: //export gogpgme_seekfunc