In this part we will add a chat application connected to a database. The database we will use is mongodb, so go ahead and install that one now, in Ubuntu it is available through apt as mongodb.
First let's add the line
tm["chat"] = template.Must(template.ParseFiles("templates/chat.gohtml", "templates/base.gohtml"))
Then we add the following template file:
{{define "title"}}Home{{end}}
{{define "body"}}
<h1>Welcome to the chat app.</h1>
<form action="/chat/" method="POST">
<input type="text" name="message" placeholder="Message" autofocus autocomplete="off">
<input type="submit" name="submit-btn" value="Send">
</form>
{{range .Msgs}}
{{.Author}} said "{{.Message}}" at {{.Time}}<br>
{{end}}
{{end}}
Next we add
router.HandleFunc("/chat/", serveChat).Methods("GET")
func serveChat(w http.ResponseWriter, r *http.Request) {
dbclient := getClient()
msgs := getRecentMessages(dbclient, 30)
data := struct {
Name string
Msgs []message
}{Name: "Anon", Msgs: msgs}
err := tm["chat"].ExecuteTemplate(w, "base", data)
if err != nil {
log.Println(err)
}
}
Alright, some new stuff in this function, let us define these functions in a new file called db.go:
package main
import (
"go.mongodb.org/mongo-driver/bson"
"go.mongodb.org/mongo-driver/mongo"
"go.mongodb.org/mongo-driver/mongo/options"
"context"
"log"
"time"
)
func getClient() *mongo.Client {
ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
defer cancel()
client, err := mongo.Connect(ctx, options.Client().ApplyURI("mongodb://localhost:27017"))
if err != nil {
log.Println(err)
}
return client
}
type message struct {
Author string
Message string
Time string
}
func addChatMessage(client *mongo.Client, msg message) {
mes := bson.M{"author": msg.Author, "message": msg.Message, "time": msg.Time}
collection := client.Database("gocourse").Collection("chat")
ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
defer cancel()
_, err := collection.InsertOne(ctx, mes)
if err != nil {
log.Println(err)
}
}
func getRecentMessages(client *mongo.Client, n int64) []message {
collection := client.Database("gocourse").Collection("chat")
ctx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
defer cancel()
findOptions := options.Find()
findOptions.SetLimit(n)
findOptions.SetSort(bson.D{{Key: "_id", Value: -1}})
cur, err := collection.Find(ctx, bson.D{}, findOptions)
if err != nil {
log.Println(err)
}
defer cur.Close(ctx)
var s []message
for cur.Next(ctx) {
var result message
err := cur.Decode(&result)
if err != nil {
log.Println(err)
}
s = append(s, result)
}
if err := cur.Err(); err != nil {
log.Println(err)
}
return s
}
Now we have to handle when the user submits the form, add this line in a suitable place:
router.HandleFunc("/chat/", handleChatMessage).Methods("POST")
func handleChatMessage(w http.ResponseWriter, r *http.Request) {
if err := r.ParseForm(); err != nil {
fmt.Println(err)
return
}
var msg message
msg.Message = r.PostForm["message"][0]
msg.Author = "Anonymous"
msg.Time = time.Now().Format("2006-01-02 15:04:05")
addChatMessage(dbclient, msg)
http.Redirect(w, r, "/chat/", http.StatusSeeOther)
}
var dbclient = getClient()
We also have to add a link to the chat tab in base.gohtml navlist, and when we run we have to run with the command go run *.go in order to run the db file also. That's it! Now if you go to localhost:8080/chat/ you can write persistent messages! Next part we will look at authenticating users. As usual you can find the full working code at github.
Updated on 2020-11-30.