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How to set up analytics in Go

Feb 21, 2024

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Product analytics enable you to gather and analyze data about how users interact with your Go app. To show you how to set up analytics, in this tutorial we create a basic Go app, add PostHog, and use it to capture events and create insights.

1. Create a basic Go app

We start by creating a simple Go app that has two pages:

  1. A login page where a user can enter their name, email, and company name in a form.
  2. A home page that has some text and a button.

First, ensure Go is installed. Then, create a new folder for our project called go-analytics and initialize a new module. We also create files login.html and dashboard.html for our pages, as well as a main.go:

Terminal
mkdir go-analytics
cd go-analytics
go mod init go-analytics
touch login.html
touch dashboard.html
touch main.go

Then, add the basic layout for to our HTML files:

login.html
<!DOCTYPE html>
<html>
<head>
    <title>Login</title>
    <style>
        label, input, button {
            display: block;
            margin-bottom: 10px;
        }
    </style>
</head>
<body>
    <form action="/auth" method="POST">
        <label for="name">Name:</label>
        <input type="text" name="name" required>


        <label for="email">Email:</label>
        <input type="email" name="email" required>


        <label for="company_name">Company Name:</label>
        <input type="text" name="company_name" required>


        <button type="submit">Log in</button>
    </form>
</body>
</html>
dashboard.html
<!DOCTYPE html>
<html>
<head>
    <title>Dashboard</title>
    <script src="https://ajax.googleapis.com/ajax/libs/jquery/3.6.0/jquery.min.js"></script>
</head>
<body>
    <h1>Welcome, {{.Name}} from {{.CompanyName}}!</h1>
    <form id="dashboardForm" action="/api/dashboard" method="POST">
        <input type="hidden" name="email" value="{{.Email}}">
        <input type="hidden" name="name" value="{{.Name}}">
        <input type="hidden" name="company_name" value="{{.CompanyName}}">
        <button type="submit">Click Me</button>
    </form>


    <script>
        $(document).ready(function() {
            $('#dashboardForm').on('submit', function(e) {
                e.preventDefault();
                $.ajax({
                    url: $(this).attr('action'),
                    type: 'POST',
                    data: $(this).serialize(),
                });
            });
        });
    </script>
</body>
</html>

Next, we install the gorilla/sessions package to manage our sessions:

Terminal
go get github.com/gorilla/sessions

Lastly, we set up main.go with all our route handling:

main.go
package main


import (
    "html/template"
    "net/http"
    "github.com/gorilla/sessions"
)


var (
    store = sessions.NewCookieStore([]byte("your-secret-key"))
    templates = template.Must(template.ParseGlob("*.html"))
)


func main() {
    http.HandleFunc("/", loginHandler)
    http.HandleFunc("/auth", authHandler)
    http.HandleFunc("/dashboard", dashboardHandler)
    http.HandleFunc("/api/dashboard", apiDashboardHandler)


    http.ListenAndServe(":8000", nil)
}


func loginHandler(w http.ResponseWriter, r *http.Request) {
    templates.ExecuteTemplate(w, "login.html", nil)
}


func authHandler(w http.ResponseWriter, r *http.Request) {
    session, _ := store.Get(r, "session-name")


    session.Values["email"] = r.FormValue("email")
    session.Values["name"] = r.FormValue("name")
    session.Values["company_name"] = r.FormValue("company_name")
    session.Save(r, w)


    http.Redirect(w, r, "/dashboard", http.StatusFound)
}


func dashboardHandler(w http.ResponseWriter, r *http.Request) {
    session, _ := store.Get(r, "session-name")
    data := map[string]interface{}{
        "Email": session.Values["email"],
        "Name": session.Values["name"],
        "CompanyName": session.Values["company_name"],
    }
    templates.ExecuteTemplate(w, "dashboard.html", data)
}


func apiDashboardHandler(w http.ResponseWriter, r *http.Request) {
    // This API is called when the button is pressed
    // We'll add code later in the tutorial
}

Run go run main.go and navigate to http://localhost:8000 to see our app in action. Enter anything on the login page to save some session details.

2. Add PostHog to your app

With our app set up, it’s time to install and set up PostHog. If you don't have a PostHog instance, you can sign up for free.

Run go get github.com/posthog/posthog-go to add PostHog's Go SDK as a dependency. Then, initialize PostHog in the main() method in main.go.

To do this, you need your project API key and instance address from your project settings. You also need to create a personal API key. Use these values to initialize your client using posthog.NewWithConfig():

main.go
package main


import (
    "html/template"
    "net/http"


    "github.com/gorilla/sessions"
    "github.com/posthog/posthog-go"
)


var (
    store = sessions.NewCookieStore([]byte("your-secret-key"))
    templates = template.Must(template.ParseGlob("*.html"))
    client posthog.Client // declare the PostHog client as a global variable
)


func main() {
     client, _ = posthog.NewWithConfig(
       "<ph_project_api_key>",
       posthog.Config{
           PersonalApiKey: "<ph_personal_api_key>",
           Endpoint: "<ph_client_api_host>",
       },
     )
     defer client.Close()


    http.HandleFunc("/", loginHandler)
    http.HandleFunc("/auth", authHandler)
    http.HandleFunc("/dashboard", dashboardHandler)
    http.HandleFunc("/api/dashboard", apiDashboardHandler)


    http.ListenAndServe(":8000", nil)
}

With this set up, we're ready to capture events.

3. Implement the event capture code

To show how to capture events with PostHog, we capture an event when the button on the dashboard page is clicked. To do this, we call posthog.Capture:

main.go
func apiDashboardHandler(w http.ResponseWriter, r *http.Request) {
    email := r.FormValue("email")
    client.Enqueue(posthog.Capture{
        DistinctId: email,
        Event:      "home_api_called",
    })
}

With this set up, refresh your app and click the button on the dashboard page a few times. You should now see the captured event in your PostHog activity tab.

Events in PostHog

💡 PostHog tip: Setting the correct DistinctId

When calling posthog.Capture, you need to provide a DistinctId argument. This is a unique identifier for your user and enables you to correctly attribute events to them.

For logged-in users, you typically use their email or database ID. For logged-out or anonymous users, you should use a unique identifier, either generated by you or the PostHog JavaScript web library (which can then be accessed in the cookies. See an example of accessing the PostHog cookie in our Nuxt tutorial).

Setting event properties

When capturing events, you can optionally include additional information by setting the properties argument. This is helpful for breaking down or filtering events when creating insights.

As an example, we can add the user's name as an event property:

main.go
func apiDashboardHandler(w http.ResponseWriter, r *http.Request) {
    email := r.FormValue("email")
    name := r.FormValue("name")
    client.Enqueue(posthog.Capture{
        DistinctId: email,
        Event:      "home_api_called",
        Properties: posthog.NewProperties().
            Set("user_name", name),
    })
}

Capturing group events

Groups are a powerful feature in PostHog that aggregate events based on entities, such as organizations or companies. This is especially helpful for B2B SaaS apps, where often you want to view insights such as number of active companies or company churn rate.

To enable group analytics, you'll need to upgrade your PostHog account to include them. This requires entering your credit card, but don't worry, we have a generous free tier of 1 million events per month – so you won't be charged anything yet.

To create groups in PostHog, simply include them in your code when capturing events by setting the $groups argument:

main.go
func apiDashboardHandler(w http.ResponseWriter, r *http.Request) {
    email := r.FormValue("email")
    name := r.FormValue("name")
    companyName := r.FormValue("company_name")
    client.Enqueue(posthog.Capture{
        DistinctId: email,
        Event:      "home_api_called",
        Properties: posthog.NewProperties().
            Set("user_name", name),
        Groups: posthog.NewGroups().
            Set("company", companyName),
    })
}

In the above example, we create a group type company, and then set the value as the unique identifier for that specific company. This enables us to breakdown insights by company (we show you how to do this in the next section).

4. Create an insight in PostHog

Restart your app and capture events using different inputs in the login page. This will capture events for different users and companies and enable us to show the power of PostHog insights.

Next, go to the Product analytics tab in PostHog and click the + New insight button. PostHog supports many different types of insights, such as trends, funnels, paths and more.

In this tutorial, we create a simple trend insight:

  1. Select the Trends tab.
  2. Under the Series header select the home_api_called event.
  3. Click the Total count dropdown to change how events are aggregated. You can choose options such as Count per user, Unique users, Unique company(s), and more. You can also add filters or breakdown based on properties.

For example, in the image below we set our insight to show number of unique users that captured the home_api_called event where the user_name property is equal to Max:

Insight created in PostHog

That's it! Feel free to play around in your dashboard and explore the different kinds of insights you can create in PostHog.

Further reading