You will need Go, and SQLite installed on your machine. Basic knowledge of Go and JavaScript will be helpful. The internet is a breeding ground for all kinds of social activities because it expands the possibilities of communication. In order to keep web applications social and enjoyable, it is important for them to have one or more interfaces for the users to interact through. One such interface is the comment section. The comment section is where users can discuss a subject (post, video, picture) that they have access to. In the past, for a user to see a comment from another user, the user would have to refresh the browser window. However, with realtime comments now we can automatically pull in comments live. This article will cover how we can build realtime commenting using Pusher. By the end of this article, we will have built an application that looks like this: Requirements To follow along with this article, you will need the following: Go (version >= 0.10.x) installed on your computer. Heres how you can . install Go SQLite (v3.x) installed on your machine. . Installation guide Basic knowledge of the Go programming language. Basic knowledge of JavaScript (ES6). Basic knowledge of Vue.js. Getting a Pusher Channels application The first step will be to get a Pusher Channels application. We will need the application credentials for our realtime features to work. Go to the Pusher website and create an account. After creating an account, you should create a new application. Follow the application creation wizard and then you should be given your application credentials, we will use this later in the article. Now that we have our application, let’s move on to the next step. Setting up the codebase Let’s start by navigating into the directory located in the . Then we’ll create a new directory for our app there. src $GOPATH $ cd $GOPATH/src$ mkdir go-realtime-comments$ cd go-realtime-comments Create a file in this directory. comments.go Before we write code, we need to import a few Go packages that will help run our projects. We will install the and the . Run the following commands to pull in the packages: Echo framework SQLite packages $ go get github.com/labstack/echo$ go get github.com/labstack/echo/middleware$ go get github.com/mattn/go-sqlite3 ⚠️ If you use Windows and you encounter the error ‘cc.exe: sorry, unimplemented: 64-bit mode not compiled in ‘, then you need a Windows gcc port, such as https://sourceforge.net/projects/mingw-w64/ . Also see this GitHub issue . With your favorite editor, open the file and paste in the following lines of code: comments.go package main import (// "database/sql" "github.com/labstack/echo" "github.com/labstack/echo/middleware" // \_ "github.com/mattn/go-sqlite3" ) Configuring the database and routes Every Go application must have a function. This is where the execution of the application will start from, so let’s create our function: main main In the file, add the following below the imports: comments.go func main() { // Echo instance e := echo.New() // Middleware e.Use(middleware.Logger()) e.Use(middleware.Recover()) // Define the HTTP routes e.GET("/comments", func(c echo.Context) error { return c.JSON(200, "GET Comments") }) e.POST("/comment", func(c echo.Context) error { return c.JSON(200, "POST a new Comment") }) // Start server e.Logger.Fatal(e.Start(":9000")) } In the main function, we have defined some basic route handler functions, these functions basically return hard-coded text to the browser on request. The last line will start Go’s standard HTTP server using Echo’s start method and listen for requests port 9000. We can test that the application works at this stage by running it and making some requests using . Postman Here is how you can run the application: $ go run ./comments.go We can send HTTP requests using Postman. Here’s a sample GET request using Postman: POST request with Postman: We will create a function that will initialize a database and for that, we need the SQL and SQLite3 drivers. We already added them to the statement so uncomment them. We will also create a function that will migrate the database using a database schema defined inside the function. import Open the file and paste the following code before the function: comments.go main func initDB(filepath string) *sql.DB {db, err := sql.Open("sqlite3", filepath)if err != nil {panic(err)} if db == nil {panic("db nil")}return db} func migrate(db *sql.DB) {sql := `CREATE TABLE IF NOT EXISTS comments(id INTEGER NOT NULL PRIMARY KEY AUTOINCREMENT,name VARCHAR NOT NULL,email VARCHAR NOT NULL,comment VARCHAR NOT NULL);`_, err := db.Exec(sql)if err != nil {panic(err)}} Next, add the following code to the top of the function: main // [...] // Initialize the databasedb := initDB("storage.db")migrate(db) // [...] We can now check that these functions are being called and the database is created during execution by running the application: $ go run comments.go ⚠️ If you were already running the Go application you would need to kill the process using ctrl+c on your keyboard and then restart it to see changes. When the application is run for the first time, a file will be created in the working directory if it did not previously exist. storage.db Setting up the handlers We have tested that our application listens on the specified port 9000 and handles the HTTP requests as we configured it to. However, the current handler functions simply return hard-coded text to the browser so let’s create new handler functions to handle responses to the routes. Create a new folder in the root directory named : handlers $ mkdir handlers$ cd handlers Next, create a file and paste the following: handlers.go package handlers import ("database/sql""go-realtime-comments/models""net/http""github.com/labstack/echo") Now we need to go back to the file and import the handlers package: comments.go import ("go-realtime-comments/handlers" // \[...\] ) In the same file, replace the route definitions from earlier with the ones below: // [...] // Define the HTTP routese.File("/", "public/index.html")e.GET("/comments", handlers.GetComments(db))e.POST("/comment", handlers.PushComment(db)) // [...] Next, paste the following code in the file below the import statement: handlers.go type H map[string]interface{} // GetComments handles the HTTP request that hits the /comments endpointfunc GetComments(db *sql.DB) echo.HandlerFunc {return func(c echo.Context) error {return c.JSON(http.StatusOK, models.GetComments(db))}} func PushComment(db *sql.DB) echo.HandlerFunc {return func(c echo.Context) error {var comment models.Comment c.Bind(&comment) id, err := models.PushComment(db, comment.Name, comment.Email, comment.Comment) if err == nil { return c.JSON(http.StatusCreated, H{ "created": id, }) } return err } } The function fetches and returns comments from the database while the saves comments to the database and returns a response. GetComments PushComment Setting up the models To create the model package, we need to create a new folder in the root directory of our application: $ mkdir models$ cd models Next, create a file and paste the following code: models.go package models import ("database/sql" \_ "github.com/mattn/go-sqlite3" ) Let’s create a Comment , which is a struct with four fields: type - the ID of the comment. ID - the username of the user who made the comment. Name - the email of the user who made the comment. Email - the comment. Comment In Go, we can add metadata to variables by putting them within backticks. We can use this to define what each field should look like when converted to . This will also help the function know how to map data when registering a new comment. JSON c.Bind JSON Let’s define the structs for and . In the file paste in the following below the imports: Comment CommentCollection models.go type Comment struct {ID int `json:"id"`Name string `json:"name"`Email string `json:"email"`Comment string `json:"comment"`} type CommentCollection struct {Comments []Comment `json:"items"`} Next, paste in the following code after the structs: func GetComments(db *sql.DB) CommentCollection {sql := "SELECT * FROM comments"rows, err := db.Query(sql) if err != nil { panic(err) } defer rows.Close() result := CommentCollection{} for rows.Next() { comment := Comment{} err2 := rows.Scan(&comment.ID, &comment.Name, &comment.Email, &comment.Comment) if err2 != nil { panic(err2) } result.Comments = append(result.Comments, comment) } return result } The function is responsible for retrieving all the available comments from the database and returning them as an instance of the that we defined. GetComments CommentCollection Next, paste in the following code below the one above: func PushComment(db *sql.DB, name string, email string, comment string) (int64, error) {sql := "INSERT INTO comments(name, email, comment) VALUES(?, ?, ?)"stmt, err := db.Prepare(sql)if err != nil {panic(err)} defer stmt.Close() result, err2 := stmt.Exec(name, email, comment) if err2 != nil { panic(err2) } return result.LastInsertId() } The function adds a new comment to the database. PushComments Building the frontend Next, create a folder in our application’s root directory and create an file inside it. public index.html Open the file and paste in this code: index.html <!DOCTYPE html><html lang="en"><head><meta charset="UTF-8"><meta name="viewport" content="width=device-width, initial-scale=1.0"><meta http-equiv="X-UA-Compatible" content="ie=edge"><link rel="stylesheet" href=" " integrity="sha384-PsH8R72JQ3SOdhVi3uxftmaW6Vc51MKb0q5P2rRUpPvrszuE4W1povHYgTpBfshb" crossorigin="anonymous"><title>Realtime comments</title><script src=" "></script><script src=" "></script><style> (min-width: 48em) {html {font-size: 18px;}}body {font-family: Georgia, "Times New Roman", Times, serif;color: #555;}h1, .h1, h2, .h2, h3, .h3, h4, .h4, h5, .h5, h6, .h6 {font-family: "Helvetica Neue", Helvetica, Arial, sans-serif;font-weight: 400;color: #333;}.blog-masthead {margin-bottom: 3rem;background-color: #428bca;box-shadow: inset 0 -.1rem .25rem rgba(0,0,0,.1);}.nav-link {position: relative;padding: 1rem;font-weight: 500;color: #cdddeb;}.nav-link:hover, .nav-link:focus {color: #fff;background-color: transparent;}.nav-link.active {color: #fff;}.nav-link.active::after {position: absolute;bottom: 0;left: 50%;width: 0;height: 0;margin-left: -.3rem;vertical-align: middle;content: "";border-right: .3rem solid transparent;border-bottom: .3rem solid;border-left: .3rem solid transparent;} (min-width: 40em) {.blog-title {font-size: 3.5rem;}}.sidebar-module {padding: 1rem;}.sidebar-module-inset {padding: 1rem;background-color: #f5f5f5;border-radius: .25rem;}.sidebar-module-inset p:last-child,.sidebar-module-inset ul:last-child,.sidebar-module-inset ol:last-child {margin-bottom: 0;}.blog-post {margin-bottom: 4rem;}.blog-post-title {margin-bottom: .25rem;font-size: 2.5rem;text-align: center;}.blog-post-meta {margin-bottom: 1.25rem;color: #999;text-align: center;}.blog-footer {padding: 2.5rem 0;color: #999;text-align: center;background-color: #f9f9f9;border-top: .05rem solid #e5e5e5;}.blog-footer p:last-child {margin-bottom: 0;}input{width: 45% !important;display: inline-block !important;}textarea {width: 90%;height: 150px;padding: 12px 20px;box-sizing: border-box;border: 2px solid #ccc;border-radius: 4px;background-color: #f8f8f8;resize: none;}textarea:focus, input:focus{outline: none !important;}#comment-section{background: rgb(178, 191, 214);padding: 0.5em 2em; width: 90%;margin: 10px 0;border-radius: 15px;}#comment-section > div > p {color: black;display:inline;}img{border-radius: 50%;float: left;}</style></head><body><div id="app"><header><div class="blog-masthead"><div class="container"><nav class="nav"><a class="nav-link active" href="#">Home</a></nav></div></div></header> https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0-beta.2/css/bootstrap.min.css https://unpkg.com/axios/dist/axios.min.js https://cdn.jsdelivr.net/npm/vue@2.5.16/dist/vue.js @media @media <main role="main" class="container"> <div class="row"> <div class="col-sm-12 blog-main"> <div class="blog-post"><h2 class="blog-post-title">Realtime Comments With Pusher</h2><p class="blog-post-meta">January 1, 2018 by <a href="#">Jordan</a></p><p>This blog post shows a few different types of content that's supported and styled with Bootstrap. Basic typography, images, and code are all supported.This blog post shows a few different types of content that's supported and styled with Bootstrap. Basic typography, images, and code are all supported</p><div class="comment-section"><form class="form-signin"><h5 class="comment">Comment</h5><input type="username" ref="username" class="form-control" placeholder="John Doe" required autofocus><input type="email" ref="email" class="form-control" placeholder=" " required><textarea ref="comment"></textarea><button class="btn btn-lg btn-primary" .prevent="sendComment" type="submit">Comment</button></form><br><div id="comment-section" v-for="comment in comments"><div><img src=" " width="65px" height="65px"><p> {{comment.name}} < {{comment.email}} ></p><hr></div><p style="color:black">{{comment.comment}}</p></div></div></div></div> Johndoe@gmail.com @click http://merritos.com/img/team/maleTeam.jpg </div> </main> <footer class="blog-footer"><p><a href="#">Back to top</a></p></footer> </div></body></html> Now in the same file, paste the following code before the closing tag of the HTML: body <script>var app = new Vue({el: '#app',data: {comments : []},created: function() {axios.get('/comments').then(response => {this.comments = response.data.items ? response.data.items : []})},methods: {sendComment: function(index) {let comment = {name: this.$refs.username.value,email: this.$refs.email.value,comment: this.$refs.comment.value} axios.post('/comment', comment).then(response => {this.$refs.username.value = '',this.$refs.email.value = '',this.$refs.comment.value = ''})}}})</script> Above we have the Vue.js code for our application and this is a summary of what it does: We instantiate a comments array that will hold all the available comments. In the method, we use to pull in all the comments available from the API and store it in the array. created() Axios comments In the method, we send a request to the API to create a new . sendComment comment We can build our application at this stage and visit , we should see this: http://localhost:9000 $ go run comments.go Our application should display like this: Making comments display in realtime The next thing we need to do is make sure the comments are displayed in realtime. To do this, we need to trigger an event every time a new comment is added. We will do this in the backend using the . Pusher Go library To pull in the Pusher Go library run the following command: $ go get github.com/pusher/pusher-http-go Next, let’s import the library. In our file do the following in the imports statement: models.go package models import (// [...] pusher "github.com/pusher/pusher-http-go" ) In the same file, before the definition, paste in the following code: type // [...] var client = pusher.Client{AppId: "PUSHER_APP_ID",Key: "PUSHER_APP_KEY",Secret: "PUSHER_APP_SECRET",Cluster: "PUSHER_APP_CLUSTER",Secure: true,} // [...] Here, we have initialized the Pusher client using the credentials from our earlier created app. ⚠️ Replace _PUSHER_APP_*_ keys with your Pusher app credentials. Next, let’s trigger an event every time a comment is saved to the database. Replace the function with the following code: PushComment func PushComment(db *sql.DB, name string, email string, comment string) (int64, error) {sql := "INSERT INTO comments(name, email, comment) VALUES(?, ?, ?)"stmt, err := db.Prepare(sql)if err != nil {panic(err)} defer stmt.Close() result, err2 := stmt.Exec(name, email, comment) if err2 != nil { panic(err2) } newComment := Comment{ Name: name, Email: email, Comment: comment, } client.Trigger("comment-channel", "new-comment", newComment) return result.LastInsertId() } In this newer version of the function, we create a object that holds information for the last comment that was saved to the database. Whenever a new comment is created, we will send it to the Pusher channel to be triggered on the event . newComment comment-channel new-comment To receive comments we have to register the in our frontend code. Add this line of code inside the head tag of our HTML in the index.html file: Displaying data in realtime on the client Pusher JavaScript Client <script src="https://js.pusher.com/4.1/pusher.min.js"></script> Next, we will register a Pusher instance in the life cycle hook: created() created: function() {const pusher = new Pusher('PUSHER_APP_KEY', {cluster: 'PUSHER_APP_CLUSTER',encrypted: true}); const channel = pusher.subscribe('comment-channel'); channel.bind('new-comment', data => { this.comments.push(data) }); // \[...\] } ⚠️ Replace the _PUSHER_APP_*_ keys with the credentials for your Pusher application In the code above, we are creating a Pusher instance and then subscribing to a channel. In that channel, we are listening for the event. new-comment Now we can run our application: $ go run comments.go We can point a web browser to this address and we should see the application in action: http://localhost:9000 Conclusion In this article, we looked at how to build a realtime comment system using Go, Vue.js, and Pusher Channels. The source code to the application is available on GitHub. This post first appeared on the . Pusher blog
