go-app: A Go repository from antboard

go-app is a package to build progressive web apps (PWA) with Go programming language and WebAssembly.

It uses a declarative syntax that allows creating and dealing with HTML elements only by using Go, and without writing any HTML markup.

The package also provides an http.handler ready to serve all the required resources to run Go-based progressive web apps.

Install

go-app requirements:

Go 1.14 or newer
Go module

# Init go module (if not initialized):
go mod init

# Get package:
go get -u -v github.com/maxence-charriere/go-app/v7

How it works

Users: The users of your app. They request pages and resources from their web browser.
app.Handler: An http.Handler used by your server or cloud function. It serves your app, its static resources, and all the required files to make it work on user browsers.
Application: Your app built with this package. It is built as a WebAssembly (.wasm) binary and is served by the app.Handler.
Other static resources: Styles, images, and scripts used by your app. They are also served by the app.Handler.

Declarative syntax

go-app uses a declarative syntax so you can write component-based UI elements just by using the Go programming language.

package main

import "github.com/maxence-charriere/go-app/v7/pkg/app"

type hello struct {
    app.Compo
    name string
}

func (h *hello) Render() app.UI {
    return app.Div().Body(
        app.Main().Body(
            app.H1().Body(
                app.Text("Hello, "),
                app.If(h.name != "",
                    app.Text(h.name),
                ).Else(
                    app.Text("World"),
                ),
            ),
            app.Input().
                Value(h.name).
                Placeholder("What is your name?").
                AutoFocus(true).
                OnChange(h.OnInputChange),
        ),
    )
}

func (h *hello) OnInputChange(ctx app.Context, e app.Event) {
    h.name = ctx.JSSrc.Get("value").String()
    h.Update()
}

func main() {
    app.Route("/", &hello{})
    app.Route("/hello", &hello{})
    app.Run()
}

The app is built with the Go build tool by specifying WebAssembly as architecture and javascript as operating system:

GOARCH=wasm GOOS=js go build -o app.wasm

Note that the build output is named app.wasm because the HTTP handler expects the wasm app to be named that way in order to serve its content.

HTTP handler

Once the wasm app is built, the next step is to serve it.

This package provides an http.Handler implementation ready to serve a PWA and all the required resources to make it work in a web browser.

The handler can be used to create either a web server or a cloud function (AWS Lambda, Google Cloud function or Azure function).

package main

import (
    "net/http"

    "github.com/maxence-charriere/go-app/v7/pkg/app"
)

func main() {
    h := &app.Handler{
        Title:  "Hello Demo",
        Author: "Maxence Charriere",
    }

    if err := http.ListenAndServe(":7777", h); err != nil {
        panic(err)
    }
}

The server is built as a standard Go program:

go build

Once the server and the wasm app built, app.wasm must be moved in the web directory, located by the side of the server binary. The web directory is where to put static resources, such as the wasm app, styles, scripts, or images.

The directory should look like as the following:

.                   # Directory root
├── hello           # Server binary
├── main.go         # Server source code
└── web             # Directory for static resources
    └── app.wasm    # Wasm binary

Works on mainstream browsers

	Chrome	Edge	Firefox	Opera	Safari
Desktop	✔	✔*	✔	✔	✔
Mobile	✔	✔	✔	✔	✔

*only Chromium based Edge

Demo

The hello example introduced above:

Sources	Description
hello	Hello app.
hello-local	Hello app that runs on a local server.
hello-local-external-root	Hello app that runs on a local server but with a custom root directory.
hello-docker	Hello app that run in a Docker container.
hello-gcloud-appengine	Hello app that run on Google Cloud App Engine. See live
hello-gcloud-func	Hello app that run on Google a Cloud Function. See live