Go T(emplates)

The native Go html/template library is powerful. Template inheritance, helper functions, and proper sanitizing of HTML, CSS, and Javascript are all provided. However, using html/template requires a bit of boilerplate (and forethought) which this package provides in a clever, minimal wrapper.

1. This library is for people who want use html/template.
2. This package requires you to organize your templates on-disk in a certain, logical way.

Usage

Specify the directory containing your templates, and the file extension for template files.

templates, err := got.New("templates/", ".html")

Once loaded, rendering templates inside a handler is as easy as passing the http.ResponseWriter, template name, data, and a status.

http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
  data = struct{ Name string }{"Bob"}
  err := templates.Render(w, "home", data, http.StatusOK)

  if err != nil {
    http.Error(w, err.Error(), http.StatusInternalServerError)
  }
})

Should an error be encountered, got will prevent a partial response from being sent, allowing you to handle the error (as shown above).

Conventions

xeoncross/got expects layout files to live in one of three folders based on their usage:

• pages are the "main content" for your routes
• includes are shared code blocks such as "sidebars" or "ads"
• layouts are the different page "shells" used by pages.

Each page is the "starting" point. For example, you might have a file structure like this:

pages/
  home.html
  about.html
  profile.html
  posts.html
layouts/
  main.html
  forum.html
includes/
  sidebar.html

In this example, imagine the "profile" and "posts" page use the forum.html layout, while the "home" & "about" pages use main.html + sidebar.html. Every page has access to all includes.

The Pain Point: Inheritance

With plain html/template you can't specify a template parent from the child. Instead, you have to load templates backwards by loading the child, then having the parent template.Execute() to render the child correctly inside it.

t, _ := template.ParseFiles("base.tmpl", "about.tmpl")
t.Execute(w, nil)

• https://blog.questionable.services/article/approximating-html-template-inheritance/
• https://www.kylehq.com/2017/05/golang-templates---what-i-missed/ (gist)

Solution

We solve this problem by adding a simple template comment to the child:

{/* use mobilelayout */}

This comment is removed by html/template in the final output, but tells got to load this child template inside mobilelayout.html.

Subfolders

Simple sites can easily fit everything under the pages, includes, and layouts namespaces. However, for better organization of your HTML snippets you can also use subfolders. For example, you might have custom sidebar modules you wish to isolate to their own files. Including items in subfolders (and beyond) is as easy as regular files. Imagine you had the following file:

/templates/includes/sidebar/active_users.html

You can access this in your templates using the string includes/sidebar/active_users.

Benchmarks

This library adds almost no overhead to html/template for rendering templates. This package is all about layout conventions without interfering with performance.

$ go test -bench=. --benchmem -test.cpu=1

BenchmarkCompile         	  300000	      4079 ns/op	    1256 B/op	      30 allocs/op
BenchmarkNativeTemplates 	  300000	      4028 ns/op	    1256 B/op	      30 allocs/op

This library is as fast as html/template because the organizational sorting and inheritance calculations are performed on the initial load.

Template Functions (Recommended)

Template functions provide handy helpers for doing common tasks. The Masterminds/sprig package contains +100 helper functions (inspired by underscore.js) you can use to augment your templates.

If building HTML forms, or using the CSS framework Bootstrap, you might want to look at gobuffalo/tags for helper functions to generate HTML.

Alternatives

There are a number of template engines available should you find html/template lacking for your use case. @SlinSo has put together a good benchmark of these different template engines.