add pull sub and consumer

* add pull subscribe

* fix pullsub channel name

* fix pullsub channel name

* add check consumer

* add check consumer

* add check consumer

* add check consumer

* add check consumer

* add check consumer

* add check consumer

* add check consumer

* done add pull sub

jetstream_consumer.go

@@ -0,0 +1,31 @@
+package natsio
+
+import (
+	"errors"
+	"fmt"
+
+	"github.com/nats-io/nats.go"
+)
+
+// GetConsumerInfo ...
+func (js JetStream) GetConsumerInfo(stream, name string) (*nats.ConsumerInfo, error) {
+	return js.instance.ConsumerInfo(stream, name)
+}
+
+// AddConsumer ...
+func (js JetStream) AddConsumer(stream, subject, name string) error {
+	channel := combineStreamAndSubjectName(stream, subject)
+
+	// Add
+	_, err := js.instance.AddConsumer(stream, &nats.ConsumerConfig{
+		Durable:       name,
+		AckPolicy:     nats.AckExplicitPolicy,
+		FilterSubject: channel,
+	})
+
+	if err != nil {
+		msg := fmt.Sprintf("[NATS JETSTREAM] - add consumer %s for stream #%s error: %s", name, stream, err.Error())
+		return errors.New(msg)
+	}
+	return nil
+}

jetstream_pubsub.go

@@ -13,7 +13,7 @@ func (js JetStream) Publish(stream, subject string, payload []byte) error {
 
 	_, err := js.instance.PublishAsync(channel, payload)
 	if err != nil {
-		msg := fmt.Sprintf("[NATS JETSTREAM] - publish message to subject %s error: %s", channel, err.Error())
+		msg := fmt.Sprintf("[NATS JETSTREAM] - publish message to subject #%s error: %s", channel, err.Error())
 		return errors.New(msg)
 	}
 	return nil
@@ -30,3 +30,36 @@ func (js JetStream) Subscribe(stream, subject string, cb nats.MsgHandler) (*nats
 	}
 	return sub, nil
 }
+
+// PullSubscribe ...
+//
+// Example:
+//
+// js := natsio.GetJetStream()
+//
+// sub, err := js.PullSubscribe("A_SUBJECT", "A_SUBJECT", "A_CONSUMER")
+//
+// for {
+//   messages, err := sub.Fetch(10)
+//   // process each messages
+// }
+//
+func (js JetStream) PullSubscribe(stream, subject, consumer string) (*nats.Subscription, error) {
+	channel := combineStreamAndSubjectName(stream, subject)
+
+	// Check if consumer existed
+	con, err := js.GetConsumerInfo(stream, consumer)
+	if con == nil || err != nil {
+		msg := fmt.Sprintf("[NATS JETSTREAM] - pull subscribe consumer %s not existed in stream %s", consumer, stream)
+		return nil, errors.New(msg)
+	}
+
+	// Pull
+	sub, err := js.instance.PullSubscribe(channel, consumer)
+	if err != nil {
+		msg := fmt.Sprintf("[NATS JETSTREAM] - pull subscribe subject #%s - consumer #%s error: %s", channel, consumer, err.Error())
+		return nil, errors.New(msg)
+	}
+
+	return sub, nil
+}

jetstream_queue.go

@@ -13,7 +13,7 @@ func (js JetStream) QueueSubscribe(stream, subject, queueName string, cb nats.Ms
 
 	_, err := js.instance.QueueSubscribe(channel, queueName, cb)
 	if err != nil {
-		msg := fmt.Sprintf("[NATS JETSTREAM] - queue subscribe with subject %s error: %s", channel, err.Error())
+		msg := fmt.Sprintf("[NATS JETSTREAM] - queue subscribe with subject #%s error: %s", channel, err.Error())
 		return errors.New(msg)
 	}
 	return nil