code: func (ctx *bytesKeyIterator) GetNext() (key string, rev int64, stop bool) {
  	if ctx.index >= ctx.len {
  		return "", 0, true
  	}
  
  	key = string(ctx.resp.Kvs[ctx.index].Key)
  	rev = ctx.resp.Kvs[ctx.index].ModRevision
  	ctx.index++
  
  	return key, rev, false
  }
docs: // GetNext returns the following key (+ revision) from the result set.
  // When there are no more keys to get, <stop> is returned as *true*
  // and <key> and <rev> are default values.