As someone who actively builds applications within the JavaScript / Node.js ecosystem leveraging frameworks like Next.js, Vue, Express.js, etc., hot reloading is usually built into the framework or needs to install a package to get it up and running.

While exploring the Go ecosystem, hot reloading seems like an afterthought in most of their popular frameworks. In fact, it became a source of concern for me and led me down the rabbit hole of finding possible solutions on how to include hot reloading in my Go applications.

This guide will explore what hot reloading is and why it is needed. It will also explore two libraries to help build hot reloading into your applications.

# What is hot reloading?

Hot reloading is a technique used during application development, allowing you to observe updated changes to the source code in real-time without reloading the entire application. It preserves the application state, enabling you to continue working without losing the current state of the application. It allows you to view changes instantly, accelerating the development process and enhancing productivity.

# What are the benefits of hot reloading?

The following are the benefits of enabling hot reloading in your applications:

-   Enhanced user experience
-   Fast development
-   Minimal context switching
-   Improved feedback loop

1. **Enhanced user experience**: The ability to make changes to the codebase and see them in real-time improves the development process. With this capability, developers can rapidly prototype and design better applications.
2. **Fast development**: With hot reloading, developers don't have to manually reload the application to see the latest changes. Development time is fast because changes are reflected immediately.
3. **Minimal context switching**: A major source of distraction for developers is having to go back to the terminal to rebuild and run the application every time changes are made. However, with hot reloading, they can focus on the task without any interruptions or worries about their changes being reflected as updates occur in real-time.
4. **Improved feedback loop**: Because changes are visible in real-time, developers receive immediate feedback and can easily fix bugs, identify where the application is broken, and consequently improve the development workflow.

# How to implement hot reloading in a Go application

This section will explore two libraries that make hot reloading possible in a Go application:

-   Modd
-   Air

Before we explore how to use these libraries, let’s set up a sample Go project using the Gin-gonic framework.

Create a directory.

```bash
mkdir sample_go && cd sample_go
```

Next, initialize a Go module to manage project dependencies.

```bash
go mod init sample_go
```

Install the required dependency.

```bash
go get github.com/gin-gonic/gin
```

Create a sample application.

```go
package main

import "github.com/gin-gonic/gin"

func main() {
    r := gin.Default()
    r.GET("/", func(c *gin.Context) {
        c.JSON(200, gin.H{
            "message": "Hello world!",
        })
    })

    r.Run()
}
```

## Modd for hot reloading

[Modd](https://github.com/cortesi/modd) is a library that makes hot reloading possible in Go applications. To use it, install it on your machine using the command below:

    go install github.com/cortesi/modd/cmd/modd@latest

In your project directory, create a `modd.conf` file and add the snippet below:

```bash
**/*.go {
    prep: go test @dirmods
}
```

The command above tells **Modd** to watch for changes to any `.go` file and run the changes on `test` directories.

To enable hot reloading, run the command below in your terminal:

```bash
modd
```

> In case you get an error about `go: errors parsing go.mod: /project/path/  invalid go version '1.XX.X': must match format 1.23`. Remove the Go semantic version stated inside the `go.mod` file. For example change `go 1.22.1` to `go 1.22`

## Air for hot reloading

[Air](https://github.com/cosmtrek/air) is another library that enables hot reloading in Go applications. To use it, install it on your machine using the command below:

```
go install github.com/cosmtrek/air@latest
```

Next, initialize **Air** by running the command below:

```
air init
```

The command above will create a `.air.toml` file with default configurations to get your application up and running.

Finally, to enable hot reloading, run the command below:

```
air
```

# Conclusion

Both libraries enable hot reloading and offer extensive configuration and flexibility regarding which files and folders should be excluded or ignored, pattern matching, environment setup, and much more. To learn more, you can check out their official documentation.

Useful resources:

-   [Modd documentation](https://github.com/cortesi/modd)
-   [Air documentation](https://github.com/cosmtrek/air)


This guide will explore what hot reloading is and why it is needed. It will also explore two libraries to help build hot reloading into your applications.

How to implement hot reloading in a Go application

Go is a statically typed, compiled high-level programming language for building systems, command-line interfaces (CLI), and more. It is typically designed for use on the backend; however, there are times when you want to use the same language to build a full-stack application with a functional backend and a visual frontend.

In most cases, Go developers opt for frontend frameworks/libraries like React, Vue, Angular, etc., to build the frontend part of the application. This means they must learn JavaScript/TypeScript, framework-specific paradigms, and other frontend-related overheads.

In this guide, you’ll learn how to build a fullstack application with Go using Templ, HTMX, and Xata.

# Technology Overview

**Templ**: is a templating engine that lets you build HTML with Go. It also lets you use Go syntax like `if`, `switch`, and `for` statements to build a robust frontend. You will use Templ to build reusable components and pages for the frontend.

**HTMX**: is a frontend library that lets you access modern browser features directly using HTML rather than JavaScript. You will use HTMX to process the form submission and perform other dynamic operations.

**Xata**: is a serverless database with analytics and free-text search support that makes a wide range of applications easy to build.

# Prerequisites

To follow along with this tutorial, the following are needed:

-   [Go version 1.20 or higher installed](https://go.dev/dl/)
-   Basic understanding of Go
-   Xata account. [Signup is free](https://app.xata.io/signin?mode=signup?utm_source=fullstackwriter&utm_medium=fullstackwriter-blog)

# Getting started

To get started, you need to install Templ binary. The binary generates Go code from a Templ file.

```bash
go install github.com/a-h/templ/cmd/templ@latest
```

Create a directory.

```bash
mkdir go_fullstack && cd go_fullstack
```

Next, initialize a Go module to manage project dependencies.

```bash
go mod init go-fullstack
```

Finally, we proceed to install the required dependencies with:

```bash
go get github.com/gin-gonic/gin github.com/a-h/templ github.com/joho/godotenv
```

`github.com/gin-gonic/gin` is a framework for building web applications.

`github.com/a-h/templ` is the Templ library used in the project.

`github.com/joho/godotenv` is a library for loading environment variables.

## Structuring the application

To do this, create a `cmd`, `internals`, and `views` folder in our project directory.

`cmd` is for structuring the application entry point.

`internals` is for structuring API-related files.

`views` is for structuring frontend-related files.

# Setup the database on Xata

Log into the [Xata workspace](https://app.xata.io/workspaces) and create a `todo` database. Inside the `todo` database, create a `Todo` table and add a `description` column of type `String`.

![create project](https://paper-attachments.dropboxusercontent.com/s_724B5DB0ED02FBEDE105C37DC2102A0D29EC66EAFDCC27146EA9AEF451272040_1703592508608_Screenshot+2023-12-26+at+13.07.33.png)

## Get the Database URL and set up the API Key

To get the database URL, click the **Get code snippet** button and copy the URL. Then click the **API Key** link, add a new key, save and copy the API key.

![](https://paper-attachments.dropboxusercontent.com/s_724B5DB0ED02FBEDE105C37DC2102A0D29EC66EAFDCC27146EA9AEF451272040_1703596013324_Screenshot+2023-12-26+at+14.04.29.png)
![](https://paper-attachments.dropboxusercontent.com/s_724B5DB0ED02FBEDE105C37DC2102A0D29EC66EAFDCC27146EA9AEF451272040_1703596030165_Screenshot+2023-12-21+at+23.42.03.png)

**Setup environment variable**

Create a `.env` file in the root directory and add the copied URL and API key.

```bash
XATA_DATABASE_URL= <REPLACE WITH THE COPIED DATABASE URL>
XATA_API_KEY=<REPLACE WITH THE COPIED API KEY>
```

# Build the application Frontend

To build the frontend, you’ll use Templ and HTMX to structure the application and add dynamism to a Todo application.

## Create the application components

Inside the `views` folder, create a `components/header.templ` file and add the snippet below:

```go
package components

templ Header() {
    <head>
        <script
            src="https://unpkg.com/htmx.org@1.9.10"
            integrity="sha384-D1Kt99CQMDuVetoL1lrYwg5t+9QdHe7NLX/SoJYkXDFfX37iInKRy5xLSi8nO7UC"
            crossorigin="anonymous"
        ></script>
        <script src="https://cdn.tailwindcss.com"></script>
        <meta charset="UTF-8" />
        <meta name="viewport" content="width=device-width, initial-scale=1.0" />
        <title>GO Fullstack</title>
    </head>
}
```

The snippet creates a `Header` component and adds HTMX and TailwindCSS CDNs. TailwindCSS is a low-level framework for styling.

Next, create a `components/footer.templ` file to create the application footer and style using TailwindCSS classes.

```go
package components

templ Footer() {
    <footer class="fixed p-1 bottom-0 bg-gray-100 w-full border-t">
    <div class="rounded-lg p-4 text-xs italic text-gray-700 text-center">
        &copy; Go Fullstack
    </div>
    </footer>
}
```

Finally, create an `index.templ` file inside the same `views` folder and add the snippet below:

```go
package views

import (
    "fmt"
    "go_fullstack/views/components"
)

type Todo struct {
    Id          string
    Description string
}

templ Index(todos []*Todo) {
    <!DOCTYPE html>
    <html lang="en">
        @components.Header()
        <body>
            <main class="min-h-screen w-full">
                <nav class="flex w-full border border-b-zinc-200 px-4 py-4">
                    <h3 class="text-base lg:text-lg font-medium text-center">
                        GO Fullstack app
                    </h3>
                </nav>
                <div class="mt-6 w-full flex justify-center items-center flex-col">
                    // FORM PROCESSING
                    <form
                        hx-post="/"
                        hx-trigger="submit"
                        hx-swap="none"
                        onsubmit="reloadPage()"
                        class="w-96"
                    >
                        <textarea
                            name="description"
                            cols="30"
                            rows="2"
                            class="w-full border rounded-lg mb-2 p-4"
                            placeholder="Input todo details"
                            required
                        ></textarea>
                        <button
                            class="py-1 px-4 w-full h-10 rounded-lg text-white bg-zinc-800"
                        >
                            Create
                        </button>
                    </form>
                    <section class="border-t border-t-zinc-200 mt-6 px-2 py-4 w-96">
                        // LOOP THROUGH THE TODOS
                        <ul id="todo-list">
                            for _, todo := range todos {
                                <li class="ml-4 ml-4 border p-2 rounded-lg mb-2" id={ fmt.Sprintf("%s", todo.Id) }>
                                    <p class="font-medium text-sm">Todo item { todo.Id }</p>
                                    <p class="text-sm text-zinc-500 mb-2">
                                        { todo.Description }
                                    </p>
                                    <div class="flex gap-4 items-center mt-2">
                                        <a
                                            href="#"
                                            class="flex items-center border py-1 px-2 rounded-lg"
                                        >
                                            <p class="text-sm">Edit</p>
                                        </a>
                                        <button
                                            hx-delete={ fmt.Sprintf("/%s", todo.Id) }
                                            hx-swap="delete"
                                            hx-target={ fmt.Sprintf("#%s", todo.Id) }
                                            class="flex items-center border py-1 px-2 rounded-lg hover:bg-red-300"
                                        >
                                            <p class="text-sm">Delete</p>
                                        </button>
                                    </div>
                                </li>
                            }
                        </ul>
                    </section>
                </div>
            </main>
        </body>
        @components.Footer()
    </html>
    <script>
        function reloadPage() {
                setTimeout(function() {
            window.location.reload();
        }, 2000);
        }
    </script>
}
```

The snippet above does the following:

-   Imports the required dependencies
-   Creates a `Todo` struct to represent the response data coming from the backend
-   Creates an `Index` component that uses the `Header` and `Footer` components to structure the page. Then, it uses the HTMX attributes to process form submissions and deletion of todos by calling the respective endpoints `/` and `/{todo.Id}`

## Generating Go files from the Templ files

Next, use the Templ binary you installed earlier to Generate Go codes from the views created above by running the command below in your terminal:

```bash
templ generate
```

After you run this command, you’ll see new Go files generated for each view. You use generated file to render your frontend in next section.

![Generated files](https://paper-attachments.dropboxusercontent.com/s_F11F11938F7C8DFA1B769A23ABB6104DEEFCB6B159F515F54CB1BDB5F18F2959_1713349771513_Screenshot+2024-04-17+at+11.28.49.png)

> The generated files are not to be edited.

# Putting it together and building the backend

With that done, you can use it to build the backend and render the required page.

## Create the API models and helper function

To represent the application data, create a `model.go` file inside the `internals` folder and add the snippet below:

```go
package internals

type Todo struct {
    Id          string `json:"id,omitempty"`
    Description string `json:"description,omitempty"`
}

type TodoRequest struct {
    Description string `json:"description,omitempty"`
}

type TodoResponse struct {
    Id string `json:"id,omitempty"`
}
```

The snippet above creates a `Todo`, `TodoRequest`, and `TodoResponse` struct with the required properties to describe requests and response types.

Finally, create a `helpers.go` file with a reusable function to load environment variables.

```go
package internals

import (
    "log"
    "os"
    "github.com/joho/godotenv"
)

func GetEnvVariable(key string) string {
    err := godotenv.Load()
    if err != nil {
        log.Fatal("Error loading .env file")
    }
    return os.Getenv(key)
}
```

## Create the application and API routes

Create a `route.go` file for configuring the API routes and add the snippet below:

```go
package api

import "github.com/gin-gonic/gin"

type Config struct {
    Router *gin.Engine
}

func (app *Config) Routes() {
    //routes will come here
}
```

The snippet above does the following:

-   Imports the required dependency
-   Creates a `Config` struct with a `Router` property to configure the application methods
-   Creates a `Routes` function that takes in the `Config` struct as a pointer

## Create the API services

With that done, create a `xata_service.go` file for the application and update it by doing the following:

First, import the required dependencies and create a helper function:

```go
package internals

import (
    "bytes"
    "encoding/json"
    "fmt"
    "net/http"
)

var xataAPIKey = GetEnvVariable("XATA_API_KEY")
var baseURL = GetEnvVariable("XATA_DATABASE_URL")

func createRequest(method, url string, bodyData *bytes.Buffer) (*http.Request, error) {
    var req *http.Request
    var err error'

    if method == "GET" || method == "DELETE" || bodyData == nil {
        req, err = http.NewRequest(method, url, nil)
    } else {
        req, err = http.NewRequest(method, url, bodyData)
    }

    if err != nil {
        return nil, err
    }

    req.Header.Add("Content-Type", "application/json")
    req.Header.Add("Authorization", fmt.Sprintf("Bearer %s", xataAPIKey))

    return req, nil
}
```

The snippet above does the following:

-   Imports the required dependencies
-   Creates required environment variables
-   Creates a `createRequest` function that creates HTTP requests with the required headers

Lastly, add a `createTodoService`, `deleteTodoService`, and `getAllTodosService` methods to create, delete, and get the list of todos.

```go
//imports goes here

func createRequest(method, url string, bodyData *bytes.Buffer) (*http.Request, error) {
    //createRequest code goes here
}

func (app *Config) createTodoService(newTodo *TodoRequest) (*TodoResponse, error) {
    createTodo := TodoResponse{}
    jsonData := Todo{
        Description: newTodo.Description,
    }

    bodyData := new(bytes.Buffer)
    json.NewEncoder(bodyData).Encode(jsonData)

    fullURL := fmt.Sprintf("%s:main/tables/Todo/data", baseURL)
    req, err := createRequest("POST", fullURL, bodyData)
    if err != nil {
        return nil, err
    }

    client := &http.Client{}
    resp, err := client.Do(req)
    if err != nil {
        return nil, err
    }

    defer resp.Body.Close()
    if err := json.NewDecoder(resp.Body).Decode(&createTodo); err != nil {
        return nil, err
    }

    return &createTodo, nil
}
func (app *Config) deleteTodoService(id string) (string, error) {
    fullURL := fmt.Sprintf("%s:main/tables/Todo/data/%s", baseURL, id)
    client := &http.Client{}
    req, err := createRequest("DELETE", fullURL, nil)
    if err != nil {
        return "", err
    }

    resp, err := client.Do(req)
    if err != nil {
        return "", err
    }
    defer resp.Body.Close()

    return id, nil
}

func (app *Config) getAllTodosService() ([]*Todo, error) {
    var todos []*Todo

    fullURL := fmt.Sprintf("%s:main/tables/Todo/query", baseURL)
    client := &http.Client{}
    req, err := createRequest("POST", fullURL, nil)
    if err != nil {
        return nil, err
    }

    resp, err := client.Do(req)
    if err != nil {
        return nil, err
    }

    defer resp.Body.Close()
    var response struct {
        Records []*Todo `json:"records"`
    }

    decoder := json.NewDecoder(resp.Body)
    if err := decoder.Decode(&response); err != nil {
        return nil, err
    }

    todos = response.Records
    return todos, nil
}
```

## Create the API handlers

With that done, you can use the services to create the API handlers. Create a `handler.go` file inside `internals` folder and add the snippet below:

```go
package internals

import (
    "context"
    "fmt"
    "go_fullstack/views"
    "net/http"
    "time"
    "github.com/a-h/templ"
    "github.com/gin-gonic/gin"
)

const appTimeout = time.Second * 10

func render(ctx *gin.Context, status int, template templ.Component) error {
    ctx.Status(status)
    return template.Render(ctx.Request.Context(), ctx.Writer)
}

func (app *Config) indexPageHandler() gin.HandlerFunc {
    return func(ctx *gin.Context) {
        _, cancel := context.WithTimeout(context.Background(), appTimeout)
        defer cancel()

        todos, err := app.getAllTodosService()
        if err != nil {
            ctx.JSON(http.StatusBadRequest, err.Error())
            return
        }

        var viewsTodos []*views.Todo
        for _, todo := range todos {
            viewsTodo := &views.Todo{
                Id:          todo.Id,
                Description: todo.Description,
            }
            viewsTodos = append(viewsTodos, viewsTodo)
        }

        render(ctx, http.StatusOK, views.Index(viewsTodos))
    }
}

func (app *Config) createTodoHandler() gin.HandlerFunc {
    return func(ctx *gin.Context) {
        _, cancel := context.WithTimeout(context.Background(), appTimeout)
        description := ctx.PostForm("description")
        defer cancel()

        newTodo := TodoRequest{
            Description: description,
        }

        data, err := app.createTodoService(&newTodo)
        if err != nil {
            ctx.JSON(http.StatusBadRequest, err.Error())
            return
        }

        ctx.JSON(http.StatusCreated, data)
    }
}

func (app *Config) deleteTodoHandler() gin.HandlerFunc {
    return func(ctx *gin.Context) {
        _, cancel := context.WithTimeout(context.Background(), appTimeout)
        id := ctx.Param("id")
        defer cancel()

        data, err := app.deleteTodoService(id)
        if err != nil {
            ctx.JSON(http.StatusBadRequest, err.Error())
            return
        }

        ctx.JSON(http.StatusAccepted, fmt.Sprintf("Todo with ID: %s deleted successfully!!", data))
    }
}
```

The snippet above does the following

-   Imports the required dependencies
-   Creates a `render` function that uses the `Templ` package to render matching template
-   Creates an `indexPageHandler` function that returns a Gin-gonic handler and takes in the `Config` struct as a pointer. Inside the returned handler, use the `getAllTodosService` service to get the list of todos and then render the appropriate page using the generated code from the views package (frontend)
-   Creates a `createdTodoHandler` and `deleteProjectHandler` functions that return a Gin-gonic handler and take in the `Config` struct as a pointer. Use the service created earlier to perform the corresponding action inside the returned handler

## Update the API routes to use handlers

Update the `routes.go` file with the handlers as shown below:

```go
package internals

import (
    "github.com/gin-gonic/gin"
)

type Config struct {
    Router *gin.Engine
}

func (app *Config) Routes() {
    //views
    app.Router.GET("/", app.indexPageHandler())

    //apis
    app.Router.POST("/", app.createTodoHandler())
    app.Router.DELETE("/:id", app.deleteTodoHandler())
}
```

## Putting it all together

Create the application entry point to use to serve the routes. To do this, create a `main.go` file inside the `cmd` folder and add the snippet below:

```go
package main

import (
    "go_fullstack/internals"
    "github.com/gin-gonic/gin"
)

func main() {
    router := gin.Default()

    //initialize config
    app := internals.Config{Router: router}

    //routes
    app.Routes()

    router.Run(":8080")
}
```

The snippet above does the following:

-   Imports the required dependencies
-   Creates a Gin router using the `Default` configuration
-   Initialize the `Config` struct by passing in the `Router`
-   Adds the route and run the application on port `:8080`

With that done, you can start a development server using the command below:

    go run cmd/main.go

![](https://media.giphy.com/media/v1.Y2lkPTc5MGI3NjExdmh4OGFocG9qMndmbXpsbW1hY2Q3dXRhYjA5OG9wdXppc3d3MjRrdCZlcD12MV9pbnRlcm5hbF9naWZfYnlfaWQmY3Q9Zw/gPVi98WZGeVZuCgBG9/giphy.gif)

The complete source code can be found on [GitHub](https://github.com/Mr-Malomz/go_fullstack).

# Conclusion

This post discusses how to build a fullstack application with Go, Templ, HTMX, and Xata. You can extend the application further to support viewing and editing todos.

These resources may also be helpful:

-   [Xata documentation](https://xata.io/docs?utm_source=fullstackwriter&utm_medium=fullstackwriter-blog)
-   [Templ documentation](https://templ.guide/?utm_source=fullstackwriter&utm_medium=fullstackwriter-blog)
-   [HTMX documentation](https://htmx.org/docs/?utm_source=fullstackwriter&utm_medium=fullstackwriter-blog)
-   [Go + Xata](https://fullstackwriter.dev/post/xata-go-a-getting-started-guide?category=Golang)


In this guide, you’ll learn how to build a fullstack application with Go using Templ, HTMX, and Xata.

How to build a fullstack application with Go, Templ, and HTMX

This post discusses what Xata is and provides a detailed step-by-step guide to using it to build a basic project management application with Flutter

Xata + Flutter: A getting started guide.

This post discusses what Xata is and provides a detailed step-by-step guide to using it to build a project management API in Go.

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How to implement hot reloading in a Go application

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