Expose the shard ID in the buffer (#30)

buffer.go

@@ -8,6 +8,7 @@ type Buffer struct {
 	records             []*kinesis.Record
 	firstSequenceNumber string
 	lastSequenceNumber  string
+	shardID             string
 
 	MaxRecordCount int
 }
@@ -51,3 +52,8 @@ func (b *Buffer) FirstSeq() string {
 func (b *Buffer) LastSeq() string {
 	return b.lastSequenceNumber
 }
+
+// ShardID returns the shard ID watched by the consumer
+func (b *Buffer) ShardID() string {
+	return b.shardID
+}

consumer.go

@@ -52,6 +52,7 @@ func (c *Consumer) Start(handler Handler) {
 func (c *Consumer) handlerLoop(shardID string, handler Handler) {
 	buf := &Buffer{
 		MaxRecordCount: c.BufferSize,
+		shardID:        shardID,
 	}
 
 	params := &kinesis.GetShardIteratorInput{