code: func (db *BytesConnectionEtcd) Put(key string, binData []byte, opts ...datasync.PutOption) error {
  	return putInternal(db.Logger, db.etcdClient, db.lessor, db.opTimeout, key, binData, opts...)
  }
docs: // Put writes the provided key-value item into the data store.
  // Returns an error if the item could not be written, nil otherwise.