Connect with Go

This example connects to an Aiven for Apache Cassandra® service from Go as the avnadmin user by making use of the gocql library.

Variables

These are the placeholders you will need to replace in the code sample:

Variable	Description
HOST	Host name of your Cassandra service
PORT	Port number used for connecting to your Cassandra service
USER	Username used for connecting to your Cassandra service. Defaults to avnadmin
PASSWORD	Password of the avnadmin user
SSL-CERTFILE	Path to the CA Certificate file of your Cassandra service

Prerequisites

Get the gocql library:

go get github.com/gocql/gocql

Code

1. Create a new file named main.go and add the following content:

   package main
   
   import (
   	"flag"
   	"fmt"
   	"log"
   	"time"
   
   	"github.com/gocql/gocql"
   )
   
   func main() {
   	var args = parseArgs()
   	cassandraExample(args)
   }
   
   type Args struct {
   	Host        string
   	Port        int
   	Username    string
   	Password    string
   	SSLCertfile string
   }
   
   func parseArgs() Args {
   	var args Args
   	flag.StringVar(&args.Host, "host", "", "Cassandra host")
   	flag.IntVar(&args.Port, "port", -1, "Cassandra port")
   	flag.StringVar(&args.Username, "user", "avnadmin", "Cassandra username")
   	flag.StringVar(&args.Password, "password", "", "Cassandra password")
   	flag.StringVar(&args.SSLCertfile, "ssl-certfile", "./ca.pem", "Path to project CA certificate")
   	flag.Parse()
   
   	if args.Host == "" {
   		fail("-host is required")
   	} else if args.Port == -1 {
   		fail("-port is required")
   	} else if args.Password == "" {
   		fail("-password is required")
   	}
   	return args
   }
   
   func fail(message string) {
   	flag.Usage()
   	log.Fatal(message)
   }
   
   func cassandraExample(args Args) {
   	var session = createSession(args)
   	defer session.Close()
   	createSchema(session)
   	writeData(session)
   	readData(session)
   }
   
   func createSession(args Args) gocql.Session {
   	cluster := gocql.NewCluster(args.Host)
   	cluster.ConnectTimeout = 10 * time.Second
   	cluster.Port = args.Port
   	cluster.ProtoVersion = 4
   	cluster.Authenticator = gocql.PasswordAuthenticator{
   		Username: args.Username,
   		Password: args.Password,
   	}
   	cluster.SslOpts = &gocql.SslOptions{
   		CaPath: args.SSLCertfile,
   	}
   	cluster.Consistency = gocql.Quorum
   
   	session, err := cluster.CreateSession()
   	if err != nil {
   		log.Fatal(err)
   	}
   	return *session
   }
   
   func createSchema(session gocql.Session) {
   	if err := session.Query(
   		"CREATE KEYSPACE IF NOT EXISTS example_keyspace WITH REPLICATION = {'class': 'NetworkTopologyStrategy', 'aiven': 3}",
   	).Exec(); err != nil {
   		log.Fatal(err)
   	}
   	if err := session.Query(
   		"CREATE TABLE IF NOT EXISTS example_keyspace.example_go (id int PRIMARY KEY, message text)",
   	).Exec(); err != nil {
   		log.Fatal(err)
   	}
   }
   
   func writeData(session gocql.Session) {
   	if err := session.Query(
   		"INSERT INTO example_keyspace.example_go (id, message) VALUES (?, ?)", 1, "hello world",
   	).Exec(); err != nil {
   		log.Fatal(err)
   	}
   }
   
   func readData(session gocql.Session) {
   	iter := session.Query("SELECT id, message FROM example_keyspace.example_go").Iter()
   	var id int
   	var message string
   	for iter.Scan(&id, &message) {
   		fmt.Printf("Row: id = %d, message = %s\n", id, message)
   	}
   	if err := iter.Close(); err != nil {
   		log.Fatal(err)
   	}
   }

   This code first creates a keyspace named example_keyspace and a table named example_go that contains an id and a message. Then, it writes a new entry into the table with the values 1. and hello world`. Finally, it reads the entry from the table and prints it.

2. Execute the following from a terminal window to build an executable:

   go build main.go

3. Run the program with the required flags to pass the necessary connection details:

   ./main --host <HOST> --port <PORT> --user avnadmin --password <PASSWORD> --ssl-certfile <PATH TO CERTFILE>