code: func (conn *BytesManualConnectionStr) SendSyncStringToPartition(topic string, partition int32, key string, value string) (offset int64, err error) {
  	return conn.SendSyncMessageToPartition(topic, partition, sarama.StringEncoder(key), sarama.StringEncoder(value))
  }
docs: // SendSyncStringToPartition sends a message that uses string encoder using the sync API to custom partition