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

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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

Note:

Organizations without billing information on file can only create one CockroachDB Basic cluster.

If you haven't already, sign up for a CockroachDB Cloud account.
Log in to your CockroachDB Cloud account.
On the Clusters page, click Create cluster.
On the Select a plan page, select Basic.
On the Cloud & Regions page, select a cloud provider (GCP or AWS) in the Cloud provider section.
In the Regions section, select a region for the cluster. Refer to CockroachDB Cloud Regions for the regions where CockroachDB Basic clusters can be deployed. To create a multi-region cluster, click Add region and select additional regions.
Click Next: Capacity.
On the Capacity page, select Start for free. Click Next: Finalize.
On the Finalize page, click Create cluster.

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

Set up your cluster connection

Navigate to the cluster's Overview page, and select Connect.
Under the Connection String tab, download the cluster certificate.
Take note of the connection string provided. You'll use it to connect to the database later in this tutorial.

If you haven't already, download the CockroachDB binary.
Run the cockroach start-single-node command:
```
$ cockroach start-single-node --advertise-addr 'localhost' --insecure
```
This starts an insecure, single-node cluster.

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:

$ 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:

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.

package main

import (
    "context"
    "log"
    "os"

    crdbpgx "github.com/cockroachdb/cockroach-go/v2/crdb/crdbpgxv5"
    "github.com/google/uuid"
    "github.com/jackc/pgx/v5"
)

func main() {
    // Read in connection string
    config, err := pgx.ParseConfig(os.Getenv("DATABASE_URL"))
    if err != nil {
        log.Fatalf("error parsing connection configuration: %v", err)
    }
    config.RuntimeParams["application_name"] = "$ docs_simplecrud_gopgx"
    conn, err := pgx.ConnectConfig(context.Background(), config)
    if err != nil {
        log.Fatalf("error connecting to database: %v", err)
    }
    defer conn.Close(context.Background())

    // Set up table
    err = crdbpgx.ExecuteTx(context.Background(), conn, pgx.TxOptions{}, func(tx pgx.Tx) error {
        return initTable(context.Background(), tx)
    })
    if err != nil {
        log.Fatalf("error initializing table: %v", err)
    }

    // 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.Fatalf("error insertin rows: %v", err)
    }
    log.Println("New rows created.")

    // 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.Fatalf("error transferring funds: %v", err)
    }
    log.Println("Transfer successful.")

    // 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.Fatalf("error deleting rows: %v", err)
    }
    log.Println("Rows deleted.")

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

func initTable(ctx context.Context, tx pgx.Tx) error {
    // Dropping existing table if it exists
    log.Println("Drop existing accounts table if necessary.")
    if _, err := tx.Exec(ctx, "DROP TABLE IF EXISTS accounts"); err != nil {
        return err
    }

    // Create the accounts table
    log.Println("Creating accounts table.")
    if _, err := tx.Exec(ctx,
        "CREATE TABLE accounts (id UUID PRIMARY KEY DEFAULT gen_random_uuid(), balance INT8)"); err != nil {
        return err
    }
    return nil
}

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
}

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

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

cat dbinit.sql | cockroach sql --url "<connection-string>"

Where <connection-string> is the connection string you obtained earlier from the CockroachDB Cloud Console.

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

Step 1. Start CockroachDB

Create a free cluster

Set up your cluster connection

Step 2. Get the code

Step 3. Initialize the database

Step 4. Run the code

What's next?