[Go] A simple Go server

Hello World

Let's create a simple Go server, first let's setup the server and do hello world

// @filename: main.go
package main

import (
	"fmt"
	"net/http"
)

func handleHello (res http.ResponseWriter, req *http.Request) {
    // Covert to []bytpe type
	res.Write([]byte("Hello from a Go program"))
}

func main {
    server := http.NewServeMux()
    server.HandleFunc("/hello", handleHello)
    
    err := http.ListenAndServe(":3333", server)
    if err != nil {
        fmt.Println("Server cannot start")
    }
}

After run go run ., you can visit localhost:3333/helloto see the server is running and return hello world.

Static HTML

Now let's serve a static HTML, let say we have a publicfolder with an index.htmlfile inside.

We want to serve the public files on our serve

// @filename: main.go
package main

import (
	"fmt"
	"net/http"
)

func handleHello (res http.ResponseWriter, req *http.Request) {
    // Covert to []bytpe type
	res.Write([]byte("Hello from a Go program"))
}

func main {
    server := http.NewServeMux()
    server.HandleFunc("/hello", handleHello)
    
    // Serve public files
    fs := http.FileServer(http.Dir("./public"))
    server.Handle("/", fs)
    
    err := http.ListenAndServe(":3333", server)
    if err != nil {
        fmt.Println("Server cannot start")
    }
}

Rerun the server, visit localhost:3333you should be able to see the index.html file

Data Layer

// @filename: data/exhibitions.go

package data

type Exhibition struct {
	Title string
	Description string
	Image string
	CurrentlyOpened bool
}

var list = []Exhibition{
	{
		Title:       "Life in Ancient Greek",
		Description: "Uncover the world of ancient Greece through the sculptures, tools, and jewelry found in ruins from over 2000 years ago that have been unearthed through modern science and technology.",
		Image:       "ancient-greece.png",
		CurrentlyOpened: false,
	},
	{
		Title:       "Aristotle: Life and Legacy",
		Description: "Explore the life and legacy of the great philosopher Aristotle, one of the most influential thinkers of all time. Through rare artifacts and ancient texts, learn about his ideas on ethics, politics, and metaphysics that have shaped the world for centuries.",
		Image:       "aristotle.png",
		CurrentlyOpened: true,
	},
}

func GetAll() []Exhibition {
	return list
}

func Add(exb Exhibition) {
	list = append(list, exb)
}

We can test the data layer by add two api endpoints

• GET: /api/exhibitions
• POST: /api/exhibitions/new

API Layer

// @filename: api/get.go

package api

import (
	"encoding/json"
	"net/http"
	"strconv"

	"project/museum/data"
)

func Get(w http.ResponseWriter, r *http.Request) {
    w.Header().Set("Content-Type", "application/json")
    // /api/exhibitions?id=1
    id := r.URL.Query()["id"]
    if id != nil {
        finalId, err := strconv.Atoi(id[0]) // parseInt
        if err == nil && finalId < len(data.GetAll()) {
            // Send one item back to Client using json encoder
            json.NewEncoder(w).Encode(data.GetAll()[finalId])
        } else {
            http.Error(w, "Invalid Exhibition", http.StatusBadRequest)
        }
    } else {
        // Send all item to client
        json.NewEncoder(w).Encode(data.GetAll())
    }
}

// @filename: api/post.go

package api

import (
	"encoding/json"
	"net/http"

	"project/museum/data"
)

func Post(w http.ResponseWriter, r *http.Request) {
	if r.Method == http.MethodPost {
		var item data.Exhibition
        // Read data from client
		err := json.NewDecoder(r.Body).Decode(&item)
		if err != nil {
			http.Error(w, err.Error(), http.StatusBadRequest)
			return
		}
		data.Add(item)
		w.WriteHeader(http.StatusCreated)
		w.Write(([]byte("OK")))
	} else {
		http.Error(w, "Unsupported Method", http.StatusMethodNotAllowed)
	}
}

Now we can link those two api in our server

// @filename: main.go
package main

import (
	"fmt"
	"net/http"
    
    "project/museum/api"
	"project/museum/data"
)

func handleHello (res http.ResponseWriter, req *http.Request) {
    // Covert to []bytpe type
	res.Write([]byte("Hello from a Go program"))
}

func main {
    server := http.NewServeMux()
    server.HandleFunc("/hello", handleHello)
    // Get and Post
    server.handleFunc("/api/exhibitions", api.Get)
    server.handleFunc("/api/exhibitions", api.Post)
    
    // Serve public files
    fs := http.FileServer(http.Dir("./public"))
    server.Handle("/", fs)
    
    err := http.ListenAndServe(":3333", server)
    if err != nil {
        fmt.Println("Server cannot start")
    }
}

Rerun the server, then you can use POSTMAN to check apis.

Template

Now we want to display the data in our client by using template, so that we can do server side rendering which is more performance compare to Client side data fetching + rendering

// @filename: templates/index.tmpl

<!DOCTYPE html>
<html lang="en">
  <head>
    ...
  </head>
  <body>
    <main>
      {{ range .}}
      <article
        class="{{- if .CurrentlyOpened -}} opened {{- else -}} closed {{- end -}}"
      >
        <h2>{{ .Title }}</h2>
        <p>
          {{ .Description }}
        </p>
        <img src="gallery/{{ .Image }}" fetchpriority="high" decoding="sync" />
      </article>
      {{ end }}
    </main>
  </body>
</html>

So .means the whole data, because we will return an array of object, therefore we use rangeto foreach object, so the .represent each object

And you can see, it support logic condition {{ if cond }} A {{ else }} B {{ end }}

If you want to remove all the whie space, you can use -, then it becomes {{- if .CurrentlyOpened -}} opened {{- else -}} closed {{- end -}}

Let's serve the template

// @filename: main.go

package main

import (
	"fmt"
	"net/http"
	"text/template"

	"project/museum/api"
	"project/museum/data"
)

func handleHello (res http.ResponseWriter, req *http.Request) {
	res.Write([]byte("Hello from a Go program"))
}

func handleTemplate(res http.ResponseWriter, req *http.Request) {
	html, err := template.ParseFiles("templates/index.tmpl")
	if err != nil {
		res.WriteHeader(http.StatusInternalServerError)
		res.Write([]byte("Internal Server Error"))
	
		return
	}
	// Send data to template
	html.Execute(res, data.GetAll())
}

func main() {
	// Create a route handler
	server := http.NewServeMux()
	server.HandleFunc("/hello", handleHello)
    // Get and Post
	server.HandleFunc("/api/exhibitions", api.Get)
	server.HandleFunc("/api/exhibitions/new", api.Post)
    // template
    server.HandleFunc("/templates", handleTemplate)
	// Server public files
	fs := http.FileServer(http.Dir("./public"))
	server.Handle("/", fs)

	err := http.ListenAndServe(":3333", server)
	if err != nil {
		fmt.Println("Server cannot start")
	}
}

DONE. If you change template and css, js you don't need to restart the Go server