Build a Simple CRUD Go App with CockroachDB and the Go pgx Driver

This tutorial shows you how build a simple CRUD Go application with CockroachDB and the Go pgx driver.

Step 1. Start CockroachDB

Create a free cluster

  1. If you haven't already, sign up for a CockroachDB Cloud account.
  2. Log in to your CockroachDB Cloud account.
  3. On the Clusters page, click Create Cluster.
  4. On the Create your cluster page, select Serverless.

    Unless you change your monthly budget, this cluster will be free forever.

  5. Click Create cluster.

    Your cluster will be created in a few seconds and the Create SQL user dialog will display.

Create a SQL user

The Create SQL user dialog allows you to create a new SQL user and password.

  1. Enter a username in the SQL user field or use the one provided by default.
  2. Click Generate & save password.
  3. Copy the generated password and save it in a secure location.
  4. Click Next.

    Currently, all new users are created with full privileges. For more information and to change the default settings, see Granting privileges and Using roles.

Get the connection string

The Connect to cluster dialog shows information about how to connect to your cluster.

  1. Select General connection string from the Select option dropdown.
  2. Open the General connection string section, then copy the connection string provided and save it in a secure location.

    The sample application used in this tutorial uses system CA certificates for server certificate verification, so you can skip the Download CA Cert instructions.

    Note:

    The connection string is pre-populated with your username, password, cluster name, and other details. Your password, in particular, will be provided only once. Save it in a secure place (Cockroach Labs recommends a password manager) to connect to your cluster in the future. If you forget your password, you can reset it by going to the SQL Users page.

  1. If you haven't already, download the CockroachDB binary.
  2. Run the cockroach start-single-node command:

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    $ cockroach start-single-node --advertise-addr 'localhost' --insecure
    

    This starts an insecure, single-node cluster.

  3. Take note of the following connection information in the SQL shell welcome text:

    CockroachDB node starting at 2021-08-30 17:25:30.06524 +0000 UTC (took 4.3s)
    build:               CCL v21.1.6 @ 2021/07/20 15:33:43 (go1.15.11)
    webui:               http://localhost:8080
    sql:                 postgresql://root@localhost:26257?sslmode=disable
    

    You'll use the sql connection string to connect to the cluster later in this tutorial.

Warning:

The --insecure flag used in this tutorial is intended for non-production testing only. To run CockroachDB in production, use a secure cluster instead.

Step 2. Get the code

Clone the code's GitHub repo:

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$ git clone https://github.com/cockroachlabs/example-app-go-pgx/

The project has the following directory structure:

├── README.md
├── dbinit.sql
└── main.go

The dbinit.sql file initializes the database schema that the application uses:

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CREATE TABLE accounts (
    id UUID PRIMARY KEY,
    balance INT8
);

The main.go file contains the code for INSERT, SELECT, UPDATE, and DELETE SQL operations. The file also executes the main method of the program.

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package main

import (
    "context"
    "log"
    "os"

    "github.com/cockroachdb/cockroach-go/v2/crdb/crdbpgx"
    "github.com/google/uuid"
    "github.com/jackc/pgx/v4"
)

func insertRows(ctx context.Context, tx pgx.Tx, accts [4]uuid.UUID) error {
        // Insert four rows into the "accounts" table.
        log.Println("Creating new rows...")
        if _, err := tx.Exec(ctx,
                "INSERT INTO accounts (id, balance) VALUES ($1, $2), ($3, $4), ($5, $6), ($7, $8)", accts[0], 250, accts[1], 100, accts[2], 500, accts[3], 300); err != nil {
                return err
        }
        return nil
}

func printBalances(conn *pgx.Conn) error {
        rows, err := conn.Query(context.Background(), "SELECT id, balance FROM accounts")
        if err != nil {
                log.Fatal(err)
        }
        defer rows.Close()
        for rows.Next() {
                var id uuid.UUID
                var balance int
                if err := rows.Scan(&id, &balance); err != nil {
                        log.Fatal(err)
                }
                log.Printf("%s: %d\n", id, balance)
        }
        return nil
}

func transferFunds(ctx context.Context, tx pgx.Tx, from uuid.UUID, to uuid.UUID, amount int) error {
        // Read the balance.
        var fromBalance int
        if err := tx.QueryRow(ctx,
                "SELECT balance FROM accounts WHERE id = $1", from).Scan(&fromBalance); err != nil {
                return err
        }

        if fromBalance < amount {
                log.Println("insufficient funds")
        }

        // Perform the transfer.
        log.Printf("Transferring funds from account with ID %s to account with ID %s...", from, to)
        if _, err := tx.Exec(ctx,
                "UPDATE accounts SET balance = balance - $1 WHERE id = $2", amount, from); err != nil {
                return err
        }
        if _, err := tx.Exec(ctx,
                "UPDATE accounts SET balance = balance + $1 WHERE id = $2", amount, to); err != nil {
                return err
        }
        return nil
}

func deleteRows(ctx context.Context, tx pgx.Tx, one uuid.UUID, two uuid.UUID) error {
        // Delete two rows into the "accounts" table.
        log.Printf("Deleting rows with IDs %s and %s...", one, two)
        if _, err := tx.Exec(ctx,
                "DELETE FROM accounts WHERE id IN ($1, $2)", one, two); err != nil {
                return err
        }
        return nil
}

func main() {
        // Read in connection string
        conn, err := pgx.Connect(context.Background(), os.Getenv("DATABASE_URL"))
        if err != nil {
                log.Fatal(err)
        }
        defer conn.Close(context.Background())

        // Insert initial rows
        var accounts [4]uuid.UUID
        for i := 0; i < len(accounts); i++ {
                accounts[i] = uuid.New()
        }

        err = crdbpgx.ExecuteTx(context.Background(), conn, pgx.TxOptions{}, func(tx pgx.Tx) error {
                return insertRows(context.Background(), tx, accounts)
        })
        if err == nil {
                log.Println("New rows created.")
        } else {
                log.Fatal("error: ", err)
        }

        // Print out the balances
        log.Println("Initial balances:")
        printBalances(conn)

        // Run a transfer
        err = crdbpgx.ExecuteTx(context.Background(), conn, pgx.TxOptions{}, func(tx pgx.Tx) error {
                return transferFunds(context.Background(), tx, accounts[2], accounts[1], 100)
        })
        if err == nil {
                log.Println("Transfer successful.")
        } else {
                log.Fatal("error: ", err)
        }

        // Print out the balances
        log.Println("Balances after transfer:")
        printBalances(conn)

        // Delete rows
        err = crdbpgx.ExecuteTx(context.Background(), conn, pgx.TxOptions{}, func(tx pgx.Tx) error {
                return deleteRows(context.Background(), tx, accounts[0], accounts[1])
        })
        if err == nil {
                log.Println("Rows deleted.")
        } else {
                log.Fatal("error: ", err)
        }

        // Print out the balances
        log.Println("Balances after deletion:")
        printBalances(conn)
}
Note:

CockroachDB may require the client to retry a transaction in the case of read/write contention. The CockroachDB Go client includes a generic retry function (ExecuteTx()) that runs inside a transaction and retries it as needed. The code sample shows how you can use this function to wrap SQL statements.

Step 3. Initialize the database

  1. Navigate to the example-app-go-pgx directory:

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    $ cd example-app-go-pgx
    
  2. Set the DATABASE_URL environment variable to the connection string for your cluster:

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    export DATABASE_URL="postgresql://root@localhost:26257?sslmode=disable"
    
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    export DATABASE_URL="{connection-string}"
    

    Where {connection-string} is the connection string you obtained from the CockroachDB Cloud Console.

  3. To initialize the example database, use the cockroach sql command to execute the SQL statements in the dbinit.sql file:

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    cat dbinit.sql | cockroach sql --url $DATABASE_URL
    

    The SQL statement in the initialization file should execute:

    CREATE TABLE
    
    Time: 102ms
    

Step 4. Run the code

  1. Initialize the module:

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    $ go mod init basic-sample && go mod tidy
    
  2. Run the code:

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    $ go run main.go
    

    The output should look similar to the following:

    2021/07/20 14:48:02 Creating new rows...
    2021/07/20 14:48:02 New rows created.
    2021/07/20 14:48:02 Initial balances:
    2021/07/20 14:48:02 3a936990-a0c9-45bf-bc24-92e10d91dca9: 300
    2021/07/20 14:48:02 8d1849dd-9222-4b12-a4ff-94e583b544a8: 250
    2021/07/20 14:48:02 c6ae8917-d24e-4115-b719-f663dbfb9ffb: 500
    2021/07/20 14:48:02 d0ce1f5c-e468-4899-8590-2bb6076247f2: 100
    2021/07/20 14:48:02 Transferring funds from account with ID c6ae8917-d24e-4115-b719-f663dbfb9ffb to account with ID d0ce1f5c-e468-4899-8590-2bb6076247f2...
    2021/07/20 14:48:02 Transfer successful.
    2021/07/20 14:48:02 Balances after transfer:
    2021/07/20 14:48:02 3a936990-a0c9-45bf-bc24-92e10d91dca9: 300
    2021/07/20 14:48:02 8d1849dd-9222-4b12-a4ff-94e583b544a8: 250
    2021/07/20 14:48:02 c6ae8917-d24e-4115-b719-f663dbfb9ffb: 400
    2021/07/20 14:48:02 d0ce1f5c-e468-4899-8590-2bb6076247f2: 200
    2021/07/20 14:48:02 Deleting rows with IDs 8d1849dd-9222-4b12-a4ff-94e583b544a8 and d0ce1f5c-e468-4899-8590-2bb6076247f2...
    2021/07/20 14:48:02 Rows deleted.
    2021/07/20 14:48:02 Balances after deletion:
    2021/07/20 14:48:02 3a936990-a0c9-45bf-bc24-92e10d91dca9: 300
    2021/07/20 14:48:02 c6ae8917-d24e-4115-b719-f663dbfb9ffb: 400
    

    As shown in the output, the code does the following:

    • Inserts some rows into the accounts table.
    • Reads values from the table.
    • Updates values in the table.
    • Deletes values from the table.

What's next?

Read more about using the Go pgx driver.

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