Write a Simple Go Application to work with Outlook Data on Linux

Go is an open source programming language that enables you to easily build software on Linux/UNIX machines. When Go is paired with the ODBC Driver for Outlook and unixODBC you are able write applications with connectivity to live Outlook data. This article will walk you through the process of installing the ODBC Driver for Outlook, configuring a connection using the unixODBC Driver Manager, and creating a simple Go application to work with Outlook data.

Using the CData ODBC Drivers on a Unix/Linux Machine

The CData ODBC Drivers are supported in various Red Hat-based and Debian-based systems, including Ubuntu, Debian, RHEL, CentOS, and Fedora. There are also several libraries and packages that are required, many of which may be installed by default, depending on your system. For more information on the supported versions of Linux operating systems and the required libraries, please refer to the "Getting Started" section in help documentation (installed and found online).

Installing the Driver Manager

Before installing the driver, you need to be sure that your system has a driver manager. For this article, you will use unixODBC, a free and open source ODBC driver manager that is widely supported.

For Debian-based systems like Ubuntu, you can install unixODBC with the APT package manager:

apt-get install unixodbc unixodbc-dev

For systems based on Red Hat Linux, you can install unixODBC with yum or dnf:

yum install unixODBC unixODBC-devel

The unixODBC driver manager reads information about drivers from an odbcinst.ini file and about data sources from an odbc.ini file. You can determine the location of the configuration files on your system by entering the following command into a terminal:

odbcinst -j

NOTE: You may need to install odbcinst. Use the following command in a terminal:

apt install odbcinst

The output of the command will display the locations of the configuration files for ODBC data sources and registered ODBC drivers. User data sources can only be accessed by the user account whose home folder the odbc.ini is located in. System data sources can be accessed by all users. Below is an example of the output of this command:

DRIVERS............: /etc/odbcinst.ini
SYSTEM DATA SOURCES: /etc/odbc.ini
FILE DATA SOURCES..: /etc/ODBCDataSources
USER DATA SOURCES..: /home/myuser/.odbc.ini
SQLULEN Size.......: 8
SQLLEN Size........: 8
SQLSETPOSIROW Size.: 8

Installing the Driver

You can download the driver in standard package formats: the Debian .deb package format or the .rpm file format. Once you have downloaded the file, you can install the driver from the terminal.

The driver installer registers the driver with unixODBC and creates a system DSN, which can be used later in any tools or applications that support ODBC connectivity.

For Debian-based systems like Ubuntu, run the following command with sudo or as root:

dpkg -i /path/to/package.deb

For systems that support .rpms, run the following command with sudo or as root:

rpm -i /path/to/package.rpm

Once the driver is installed, you can list the registered drivers and defined data sources using the unixODBC driver manager:

List the Registered Driver(s)

odbcinst -q -d
CData API Driver for ODBC
...

List the Defined Data Source(s)

odbcinst -q -s
CData API Source
...

To use the CData API Driver for ODBC with unixODBC, you need to ensure that the driver is configured to use UTF-16. To do so, edit the INI file for the driver (cdata.odbc.api.ini), which can be found in the lib folder in the installation location (typically /opt/cdata/cdata-odbc-driver-for-api), as follows:

cdata.odbc.api.ini

...

[Driver]
DriverManagerEncoding = UTF-16

Modifying the DSN

When the driver is installed, a system DSN should be predefined. You can modify the DSN by editing the system data sources file (/etc/odbc.ini) and defining the required connection properties. Additionally, you can create user-specific DSNs that will not require root access to modify in $HOME/.odbc.ini.

Using OAuth Authentication

Microsoft Graph API uses OAuth 2.0 for authentication. You must register an application in the Microsoft Azure Portal to obtain OAuth credentials (Client ID and Client Secret).

Obtaining OAuth Credentials

1. Log in to the Azure Portal.
2. Navigate to Azure Active Directory > App registrations.
3. Click New registration to create a new application.
4. Enter an application name and select the appropriate account types.
5. Set the Redirect URI to your application's callback URL (e.g., http://localhost:33333 for desktop apps).
6. Click Register to create the application.
7. On the application overview page, copy the Application (client) ID - this is your OAuthClientId.
8. Navigate to Certificates & secrets and create a new client secret.
9. Copy the client secret value - this is your OAuthClientSecret.
10. Navigate to API permissions and add the required Microsoft Graph API permissions:
    • Mail.Read - For accessing email messages
    • Contacts.Read - For accessing contacts
    • Calendars.Read - For accessing calendar events
    • Tasks.Read - For accessing To Do tasks
    • offline_access - For obtaining refresh tokens
11. Click Grant admin consent to grant these permissions.

Connecting with OAuth

After setting the following connection properties, you are ready to connect:

• AuthScheme: Set this to OAuth.
• InitiateOAuth: Set this to GETANDREFRESH. The CData API Profile for Outlook will automatically walk through the OAuth process in order to obtain the access token.
• OAuthClientId: Set this to the Application (client) ID from Azure Portal.
• OAuthClientSecret: Set this to the client secret value from Azure Portal.
• TenantId: Set this to your Azure AD tenant identifier (GUID or domain name like 'contoso.onmicrosoft.com').
• CallbackURL: Set this to the Redirect URI you specified in your app registration (e.g., http://localhost:33333 for desktop apps).

Example connection string

Profile=C:\profiles\Outlook.apip;AuthScheme=OAuth;InitiateOAuth=GETANDREFRESH;OAuthClientId=your_client_id;OAuthClientSecret=your_client_secret;TenantId=your_tenant_id;CallbackUrl=http://localhost:33333;

/etc/odbc.ini or $HOME/.odbc.ini

[CData API Source]
Driver = /opt/cdata/cdata-api-driver-for-api/lib/libapiodbc.x64.so
Description = My Description
Profile = C:\profiles\Outlook.apip
AuthScheme = OAuth
InitiateOAuth = GETANDREFRESH
OAuthClientId = your_client_id
OAuthClientSecret = your_client_secret
TenantId = your_tenant_id
CallbackUrl = http://localhost:33333

For specific information on using these configuration files, please refer to the help documentation (installed and found online).

Creating a Simple Go App for Outlook Data

With the Driver Manager installed and the DSN configured, you are ready to create a simple Go application to work with your Outlook data. To start, install a Go driver for ODBC databases. While there are several options available, this article will use the odbc driver found at https://github.com/alexbrainman/odbc.

Installing ODBC on Linux

There are a series of steps required to install the ODBC driver for Go.

1. Create the $HOME/golang/go path (if it does not exist) by entering the following commands in a terminal:

   mkdir /root/golang
   mkdir /root/golang/go
       

2. Define the GOPATH environment variable:

   export GOPATH=$HOME/golang/go
     

3. Create a module inside the new Go directory:

   cd $GOPATH
   go mod init myproject
       

4. Install the Go driver for ODBC databases:

   go get http://github.com/alexbrainman/odbc
     

Now you are ready to create and execute a simple Go application.

Sample Go Application

The sample application issues a simple SQL SELECT query for Outlook data and displays the results. Create the directory $GOPATH/src/cdata-odbc-outlook and create a new Go source file, copying the source code from below.

cdata-odbc-outlook.go

package main

import (
  _ "github.com/alexbrainman/odbc"
  "database/sql"
  "log"
  "fmt"
)

func main() {
  db, err := sql.Open("odbc",
    "DSN=CData API Source")
  if err != nil {
    log.Fatal(err)
  }

  var (
     string
     string
  )

  rows, err := db.Query("SELECT ,  FROM CalendarGroupCalendars WHERE CalendarGroupId = ?", "group_id")
  if err != nil {
    log.Fatal(err)
  }
  defer rows.Close()
  for rows.Next() {
    err := rows.Scan(&, &)
    if err != nil {
      log.Fatal(err)
    }
    fmt.Println(, )
  }
  err = rows.Err()
  if err != nil {
    log.Fatal(err)
  }

  defer db.Close()
}

In the terminal, navigate to the Go application directory and build the application:

go build

After the application builds, you will be able to execute the application, displaying your Outlook data:

./cdata-odbc-outlook

At this point, you have a simple Go application for working with Outlook data. From here, you can easily expand the application, adding deeper read functionality through familiar SQL queries.