How to do it...

These steps cover writing and running your application:

1. From your Terminal or console application, create a new directory called ~/projects/go-programming-cookbook/chapter12/synckafka and navigate to this directory.
2. Run this command:

$ go mod init github.com/PacktPublishing/Go-Programming-Cookbook-Second-Edition/chapter12/synckafka

You should see a file called go.mod that contains the following:

module github.com/PacktPublishing/Go-Programming-Cookbook-Second-Edition/chapter12/synckafka   

3. Copy the tests from ~/projects/go-programming-cookbook-original/chapter12/synckafka, or use this as an exercise to write some of your own code!

4. Ensure that Kafka is up and running on localhost:9092.
5. Create a file called main.go in a directory named consumer with the following content:

        package main

        import (
            "log"

            sarama "github.com/Shopify/sarama"
        )

        func main() {
            consumer, err := 
            sarama.NewConsumer([]string{"localhost:9092"}, nil)
            if err != nil {
                panic(err)
            }
            defer consumer.Close()

            partitionConsumer, err := 

           consumer.ConsumePartition("example", 0, 
            sarama.OffsetNewest)
            if err != nil {
                panic(err)
            }
            defer partitionConsumer.Close()

            for {
                msg := <-partitionConsumer.Messages()
                log.Printf("Consumed message: \"%s\" at offset: %d\n", 
                msg.Value, msg.Offset)
            }
        }

6. Create a file called main.go in a directory named producer with the following content:

        package main

        import (

           "fmt"
           "log"

            sarama "github.com/Shopify/sarama"
        )

        func sendMessage(producer sarama.SyncProducer, value string) {
            msg := &sarama.ProducerMessage{Topic: "example", Value: 
            sarama.StringEncoder(value)}
            partition, offset, err := producer.SendMessage(msg)
            if err != nil {

               log.Printf("FAILED to send message: %s\n", err)
                return
            }
            log.Printf("> message sent to partition %d at offset %d\n", 
            partition, offset)
        }

        func main() {
            producer, err := 
            sarama.NewSyncProducer([]string{"localhost:9092"}, nil)
            if err != nil {
                panic(err)
            }
            defer producer.Close()

            for i := 0; i < 10; i++ {
                sendMessage(producer, fmt.Sprintf("Message %d", i))
            }
        }

7. Navigate up a directory.
8. Run go run ./consumer.
9. In a separate Terminal from the same directory, run go run ./producer.
10. In the producer Terminal, you should see the following:

$ go run ./producer 
2017/05/07 11:50:38 > message sent to partition 0 at offset 0
2017/05/07 11:50:38 > message sent to partition 0 at offset 1
2017/05/07 11:50:38 > message sent to partition 0 at offset 2
2017/05/07 11:50:38 > message sent to partition 0 at offset 3
2017/05/07 11:50:38 > message sent to partition 0 at offset 4
2017/05/07 11:50:38 > message sent to partition 0 at offset 5
2017/05/07 11:50:38 > message sent to partition 0 at offset 6
2017/05/07 11:50:38 > message sent to partition 0 at offset 7
2017/05/07 11:50:38 > message sent to partition 0 at offset 8
2017/05/07 11:50:38 > message sent to partition 0 at offset 9

In the consumer Terminal, you should see this:

$ go run ./consumer
2017/05/07 11:50:38 Consumed message: "Message 0" at offset: 0
2017/05/07 11:50:38 Consumed message: "Message 1" at offset: 1
2017/05/07 11:50:38 Consumed message: "Message 2" at offset: 2
2017/05/07 11:50:38 Consumed message: "Message 3" at offset: 3
2017/05/07 11:50:38 Consumed message: "Message 4" at offset: 4
2017/05/07 11:50:38 Consumed message: "Message 5" at offset: 5
2017/05/07 11:50:38 Consumed message: "Message 6" at offset: 6
2017/05/07 11:50:38 Consumed message: "Message 7" at offset: 7
2017/05/07 11:50:38 Consumed message: "Message 8" at offset: 8
2017/05/07 11:50:38 Consumed message: "Message 9" at offset: 9

11. The go.mod file may be updated and the go.sum file should now be present in the top-level recipe directory.
12. If you have copied or written your own tests, go up one directory and run go test. Ensure all tests pass.