app

A WebAssembly framework to build GUI with Go, HTML and CSS.

Install

# Package sources:
go get -u -v github.com/maxence-charriere/app

# Goapp cli tool:
go get -u -v github.com/maxence-charriere/app/cmd/goapp

How it works

Project layout

root
├── cmd
│   ├── demo-server
│   │   └── main.go
│   └── demo-wasm
│       └── main.go
└── web
    ├── wasm_exec.js
    ├── style sheets...
    ├── images...
    └── etc...

This layout follows the project layout defined in golang-standards/project-layout:

• The cmd directory contains the project main applications.
• The demo directory contains the app that is compiled in wasm and that will run in the browser.
• The demo-server directory contains the server that serves the wasm app and its resources.
• The web directory contrains the app resources like style sheets (css), images and other static resources.

Project layout can be initialized by running this command in the repository root.

goapp init -v

App

The app is the Go code compiled in web assembly and executed in the browser.

// root/cmd/demo-wasm/main.go

package main

import (
    "log"

    "github.com/maxence-charriere/app"
)

type Hello struct {
    Name string
}

func (h *Hello) Render() string {
    return `
<div class="Hello">
    <h1>
        Hello
        {{if .Name}}
            {{.Name}}
        {{else}}
            world
        {{end}}!
    </h1>
    <input value="{{.Name}}" placeholder="What is your name?" onchange="{{bind "Name"}}" autofocus>
</div>
    `
}

func main() {
    app.Import(&Hello{})

    app.DefaultPath = "/hello"

    if err := app.Run(); err != nil {
        log.Print(err)
    }
}

Server

The server serves the web assembly Go program and the other resources.

// root/cmd/demo-server/main.go

package main

import (
    "fmt"
    "log"
    "net/http"
    "os"

    "github.com/maxence-charriere/app"
)

func main() {
    http.Handle("/", &app.Handler{})

    if err := http.ListenAndServe(":3000", nil); err != nil {
        log.Fatal(err)
    }
}

Build

The whole project is built with the goapp CLI tool. Goapp builds the server, the wasm app, imports the required javascript support file and puts the pieces together to provide a ready to use project.

# Get the goapp CLI tool:
go get -u github.com/maxence-charriere/app/cmd/goapp

# Builds a server ready to serve the wasm app and its resources:
goapp build -v

# Launches the server and app in the default browser:
goapp run -v -b default

Once built, the directory tree should look like:

root
├── cmd
│   ├── demo-server
│   │   └── main.go
│   └── demo-wasm
│       └── main.go
├── demo-server (server)
└── web
    ├── goapp.wasm (app)
    ├── wasm_exec.js
    ├── style sheets...
    ├── images...
    └── etc...

See the full example code and the online demo.

Support

Requires Go 1.12.

Platform	Chrome	Edge	Firefox	Safari
Desktop	✔	✖	✔	✔
Mobile	✖	✖	✖	✖

Issues:

• Go wasm currently triggers out of memory errors on mobile platforms (golang/go#27462).
• Edge does not support TextEncoder which is used by the javascript support file.