Build a Go App with CockroachDB and GORM

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

Tip:

For another use of GORM with CockroachDB, see our examples-orms repository.

Step 1. Start CockroachDB

Choose your installation method

You can install a CockroachDB serverless cluster using either the CockroachDB Cloud Console, a web-based graphical user interface (GUI) tool, or ccloud, a command-line interface (CLI) tool.

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.

Follow these steps to create a CockroachDB serverless cluster using the ccloud CLI tool.

Note:

The ccloud CLI tool is in Preview.

Install ccloud

Choose your OS:

You can install ccloud using either Homebrew or by downloading the binary.

Use Homebrew

  1. Install Homebrew.
  2. Install using the ccloud tap:

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    brew install cockroachdb/tap/ccloud
    

Download the binary

In a terminal, enter the following command to download and extract the ccloud binary and add it to your PATH:

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curl https://binaries.cockroachdb.com/ccloud/ccloud_darwin-amd64_0.2.5.tar.gz | tar -xJ && cp -i ccloud /usr/local/bin/

Use the ARM 64 binary if you have an M1 Mac:

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curl https://binaries.cockroachdb.com/ccloud/ccloud_darwin-arm64_0.2.5.tar.gz | tar -xJ && cp -i ccloud /usr/local/bin/

In a terminal, enter the following command to download and extract the ccloud binary and add it to your PATH:

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curl https://binaries.cockroachdb.com/ccloud/ccloud_linux-amd64_0.2.5.tar.gz | tar -xz && cp -i ccloud /usr/local/bin/

In a PowerShell window, enter the following command to download and extract the ccloud binary and add it to your PATH:

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$ErrorActionPreference = "Stop"; [Net.ServicePointManager]::SecurityProtocol = [Net.SecurityProtocolType]::Tls12; $ProgressPreference = 'SilentlyContinue'; $null = New-Item -Type Directory -Force $env:appdata/ccloud; Invoke-WebRequest -Uri https://binaries.cockroachdb.com/ccloud/ccloud_windows-amd64_0.2.5.zip -OutFile ccloud.zip; Expand-Archive -Force -Path ccloud.zip; Copy-Item -Force ccloud/ccloud.exe -Destination $env:appdata/ccloud; $Env:PATH += ";$env:appdata/ccloud"; # We recommend adding ";$env:appdata/ccloud" to the Path variable for your system environment. See https://docs.microsoft.com/en-us/powershell/module/microsoft.powershell.core/about/about_environment_variables#saving-changes-to-environment-variables for more information.

Run ccloud quickstart to create a new cluster, create a SQL user, and retrieve the connection string.

The easiest way of getting started with CockroachDB Cloud is to use ccloud quickstart. The ccloud quickstart command guides you through logging in to CockroachDB Cloud, creating a new CockroachDB serverless with a $0 spend limit, and connecting to the new cluster. Run ccloud quickstart and follow the instructions:

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ccloud quickstart

The ccloud quickstart command will open a browser window to log you in to CockroachDB Cloud. If you are new to CockroachDB Cloud, you can register using one of the single sign-on (SSO) options, or create a new account using an email address.

The ccloud quickstart command will prompt you for the cluster name, cloud provider, and cloud provider region, then ask if you want to connect to the cluster. Each prompt has default values that you can select, or change if you want a different option.

Select General connection string, then copy the connection string displayed and save it in a secure location. The connection string is the line starting postgresql://.

? How would you like to connect? General connection string
Retrieving cluster info: succeeded
 Downloading cluster cert to /Users/maxroach/.postgresql/root.crt: succeeded
postgresql://maxroach:ThisIsNotAGoodPassword@free-tier4.aws-us-west-2.cockroachlabs.cloud:26257/defaultdb?options=--cluster%3Ddim-dog-147&sslmode=verify-full&sslrootcert=%2FUsers%2Fmaxroach%2F.postgresql%2Froot.crt

  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-gorm

The project has the following directory structure:

├── README.md
└── main.go

The main.go file defines an Account struct that maps to a new accounts table. The file also contains some read and write database operations that are executed in the main method of the program.

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package main

import (
    "context"
    "fmt"
    "log"
    "math/rand"
    "os"
    "time"

    "github.com/cockroachdb/cockroach-go/v2/crdb/crdbgorm"
    "github.com/google/uuid"
    "gorm.io/driver/postgres"
    "gorm.io/gorm"
)

// Account is our model, which corresponds to the "accounts" table
type Account struct {
    ID      uuid.UUID `gorm:"type:uuid;default:uuid_generate_v4()"`
    Balance int
}

// The `acctIDs` global variable tracks the random IDs generated by `addAccounts`
var acctIDs []uuid.UUID

// Insert new rows into the "accounts" table
// This function generates new UUIDs and random balances for each row, and
// then it appends the ID to the `acctIDs`, which other functions use to track the IDs
func addAccounts(db *gorm.DB, numRows int, transferAmount int) error {
    log.Printf("Creating %d new accounts...", numRows)
    for i := 0; i < numRows; i++ {
        newID := uuid.New()
        newBalance := rand.Intn(10000) + transferAmount
        if err := db.Create(&Account{ID: newID, Balance: newBalance}).Error; err != nil {
            return err
        }
        acctIDs = append(acctIDs, newID)
    }
    log.Println("Accounts created.")
    return nil
}

// Transfer funds between accounts
// This function adds `amount` to the "balance" column of the row with the "id" column matching `toID`,
// and removes `amount` from the "balance" column of the row with the "id" column matching `fromID`
func transferFunds(db *gorm.DB, fromID uuid.UUID, toID uuid.UUID, amount int) error {
    log.Printf("Transferring %d from account %s to account %s...", amount, fromID, toID)
    var fromAccount Account
    var toAccount Account

    db.First(&fromAccount, fromID)
    db.First(&toAccount, toID)

    if fromAccount.Balance < amount {
        return fmt.Errorf("account %s balance %d is lower than transfer amount %d", fromAccount.ID, fromAccount.Balance, amount)
    }

    fromAccount.Balance -= amount
    toAccount.Balance += amount

    if err := db.Save(&fromAccount).Error; err != nil {
        return err
    }
    if err := db.Save(&toAccount).Error; err != nil {
        return err
    }
    log.Println("Funds transferred.")
    return nil
}

// Print IDs and balances for all rows in "accounts" table
func printBalances(db *gorm.DB) {
    var accounts []Account
    db.Find(&accounts)
    fmt.Printf("Balance at '%s':\n", time.Now())
    for _, account := range accounts {
        fmt.Printf("%s %d\n", account.ID, account.Balance)
    }
}

// Delete all rows in "accounts" table inserted by `main` (i.e., tracked by `acctIDs`)
func deleteAccounts(db *gorm.DB, accountIDs []uuid.UUID) error {
    log.Println("Deleting accounts created...")
    err := db.Where("id IN ?", accountIDs).Delete(Account{}).Error
    if err != nil {
        return err
    }
    log.Println("Accounts deleted.")
    return nil
}

func main() {

    db, err := gorm.Open(postgres.Open(os.Getenv("DATABASE_URL")+"&application_name=$ docs_simplecrud_gorm"), &gorm.Config{})
    if err != nil {
        log.Fatal(err)
    }

    // Automatically create the "accounts" table based on the `Account`
    // model.
    db.AutoMigrate(&Account{})

    // The number of initial rows to insert
    const numAccts int = 5

    // The amount to be transferred between two accounts.
    const transferAmt int = 100

    // Insert `numAccts` rows into the "accounts" table.
    // To handle potential transaction retry errors, we wrap the call
    // to `addAccounts` in `crdbgorm.ExecuteTx`, a helper function for
    // GORM which implements a retry loop
    if err := crdbgorm.ExecuteTx(context.Background(), db, nil,
        func(tx *gorm.DB) error {
            return addAccounts(db, numAccts, transferAmt)
        },
    ); err != nil {
        // For information and reference documentation, see:
        //   https://www.cockroachlabs.com/docs/stable/error-handling-and-troubleshooting.html
        fmt.Println(err)
    }

    // Print balances before transfer.
    printBalances(db)

    // Select two account IDs
    fromID := acctIDs[0]
    toID := acctIDs[0:][rand.Intn(len(acctIDs))]

    // Transfer funds between accounts.  To handle potential
    // transaction retry errors, we wrap the call to `transferFunds`
    // in `crdbgorm.ExecuteTx`
    if err := crdbgorm.ExecuteTx(context.Background(), db, nil,
        func(tx *gorm.DB) error {
            return transferFunds(tx, fromID, toID, transferAmt)
        },
    ); err != nil {
        // For information and reference documentation, see:
        //   https://www.cockroachlabs.com/docs/stable/error-handling-and-troubleshooting.html
        fmt.Println(err)
    }

    // Print balances after transfer to ensure that it worked.
    printBalances(db)

    // Delete all accounts created by the earlier call to `addAccounts`
    // To handle potential transaction retry errors, we wrap the call
    // to `deleteAccounts` in `crdbgorm.ExecuteTx`
    if err := crdbgorm.ExecuteTx(context.Background(), db, nil,
        func(tx *gorm.DB) error {
            return deleteAccounts(db, acctIDs)
        },
    ); err != nil {
        // For information and reference documentation, see:
        //   https://www.cockroachlabs.com/docs/stable/error-handling-and-troubleshooting.html
        fmt.Println(err)
    }
}

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-gorm 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 copied earlier.

Step 4. Run the code

  1. Initialize the module:

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    $ cd example-app-go-gorm
    
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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:

    2021/09/16 14:17:12 Creating 5 new accounts...
    2021/09/16 14:17:12 Accounts created.
    Balance at '2021-09-16 14:17:12.68843 -0400 EDT m=+2.760587790':
    1580d2f4-c9ec-4f26-bbe7-6a53e9aa5170 1947
    26ddc77b-8068-409b-b305-0c5d873f7c43 7987
    3d97ea5a-5108-4388-88e8-92524d5de5e8 4159
    af49831d-d637-4a20-a9a7-01e9fe4628fe 8181
    f0cc97ef-e3fe-4abb-a44a-0dd04207f7d4 2181
    2021/09/16 14:17:12 Transferring 100 from account af49831d-d637-4a20-a9a7-01e9fe4628fe to account 3d97ea5a-5108-4388-88e8-92524d5de5e8...
    2021/09/16 14:17:12 Funds transferred.
    Balance at '2021-09-16 14:17:12.759686 -0400 EDT m=+2.831841311':
    1580d2f4-c9ec-4f26-bbe7-6a53e9aa5170 1947
    26ddc77b-8068-409b-b305-0c5d873f7c43 7987
    3d97ea5a-5108-4388-88e8-92524d5de5e8 4259
    af49831d-d637-4a20-a9a7-01e9fe4628fe 8081
    f0cc97ef-e3fe-4abb-a44a-0dd04207f7d4 2181
    2021/09/16 14:17:12 Deleting accounts created...
    2021/09/16 14:17:12 Accounts deleted.
    

    The code runs a migration that creates the accounts table in the bank database, based on the Account struct defined at the top of the main.go file.

    As shown in the output, the code also 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 GORM ORM, or check out a more realistic implementation of GORM with CockroachDB in our examples-orms repository.

You might also be interested in the following pages:


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