code: func StoreCAUniqueIDToCNMap(c context.Context, mapping map[int64]string) error {
  	buf := bytes.Buffer{}
  	enc := gob.NewEncoder(&buf)
  	if err := enc.Encode(mapping); err != nil {
  		return err
  	}
  	// Note that in practice 'mapping' is usually very small, so we are not
  	// concerned about 1MB entity size limit.
  	return transient.Tag.Apply(ds.Put(c, &CAUniqueIDToCNMap{
  		GobEncodedMap: buf.Bytes(),
  	}))
  }
docs: // StoreCAUniqueIDToCNMap overwrites CAUniqueIDToCNMap with new content.