Add an option to start consuming from latest (#59)

* Add an option to client to start consuming from latest

client.go

@@ -20,6 +20,15 @@ func WithKinesis(svc kinesisiface.KinesisAPI) ClientOption {
 	}
 }
 
+// WithStartFrmLatest will make sure the client start consuming
+// events starting from the most recent event in kinesis. This
+// option discards the checkpoints.
+func WithStartFromLatest() ClientOption {
+	return func(kc *KinesisClient) {
+		kc.fromLatest = true
+	}
+}
+
 // NewKinesisClient returns client to interface with Kinesis stream
 func NewKinesisClient(opts ...ClientOption) *KinesisClient {
 	kc := &KinesisClient{}
@@ -38,6 +47,7 @@ func NewKinesisClient(opts ...ClientOption) *KinesisClient {
 // KinesisClient acts as wrapper around Kinesis client
 type KinesisClient struct {
 	svc        kinesisiface.KinesisAPI
+	fromLatest bool
 }
 
 // GetShardIDs returns shard ids in a given stream
@@ -127,7 +137,9 @@ func (c *KinesisClient) getShardIterator(streamName, shardID, lastSeqNum string)
 		StreamName: aws.String(streamName),
 	}
 
-	if lastSeqNum != "" {
+	if c.fromLatest {
+		params.ShardIteratorType = aws.String("LATEST")
+	} else if lastSeqNum != "" {
 		params.ShardIteratorType = aws.String("AFTER_SEQUENCE_NUMBER")
 		params.StartingSequenceNumber = aws.String(lastSeqNum)
 	} else {