Epic of Code

Templates

Templates provides a way to dynamically generate HTML content and serve it to clients. Go’s standard library provides text/templates and html/templates packages to work with dynamic content. These templates can then be executed with specific data to generate the final HTML output.

text/template implements data-driven templates for generating textual output whereas html/template implements data-driven templates for generating HTML output safe against code injection.

Both html/template and text/template works same except html/template is more secure. It is suggested to use html/template whenever the output is HTML.

Templates live either as strings in your code or in their own files alongside your code. Here’s a simple example:

package main
    
import (
	"net/http"
	"html/template"
)

// Page represents data for rendering the HTML page
type Page struct {
	Title   string
	Content string
}

func main() {
	// Parse the HTML template
	tmpl, err := template.New("index").Parse(`
	<!DOCTYPE html>
	<html>
	<head>
		<title>{{.Title}}</title>
	</head>
	<body>
		<h1>{{.Title}}</h1>
		<p>{{.Content}}</p>
	</body>
	</html>
	`)
	if err != nil {
		panic(err)
	}

	// Define a handler that renders the template
	http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
		// Data for rendering the page
		pageData := Page{
			Title:   "Welcome to My Website",
			Content: "This is some dynamic content.",
		}

		// Execute the template with data and write the result to the response
		err := tmpl.Execute(w, pageData)
		if err != nil {
			http.Error(w, err.Error(), http.StatusInternalServerError)
			return
		}
	})

	// Start the server
	http.ListenAndServe(":8080", nil)
}

In this example, we define an HTML template with placeholders ( {{.Title}} and {{.Content}} ). The Go program then parses and executes the template with specific data, rendering the HTML output.

Parsing Files

If you want to execute above template through HTML files, you have to first parse it then execute it.

func main() {
	// Create a new template and parse the HTML file
	tmpl, err := template.ParseFiles("index.html")
	if err != nil {
		panic(err)
	}

	// Define a handler function
	http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
		// Create data
		pageData := Page{
    			Title:   "Welcome to My Website",
    			Content: "This is some dynamic content.",
    		}

		// Execute the template and write the output to the response writer
		err := tmpl.Execute(w, pageData)
		if err != nil {
			http.Error(w, err.Error(), http.StatusInternalServerError)
			return
		}
	})

	// Start the HTTP server on port 8080
	http.ListenAndServe(":8080", nil)
}