# go-app — Build Progressive Web Apps with Go and WebAssembly

> A Go package for building progressive web apps using a declarative component model, compiling Go code to WebAssembly so your entire application logic runs in the browser with native-like performance.

## Install

Save in your project root:

# go-app — Build Progressive Web Apps with Go and WebAssembly

## Quick Use
```go
package main

import "github.com/maxence-charriere/go-app/v10/pkg/app"

type Hello struct{ app.Compo }

func (h *Hello) Render() app.UI {
    return app.H1().Text("Hello from Go!")
}

func main() {
    app.Route("/", func() app.Composer { return &Hello{} })
    app.RunWhenOnBrowser()
    http.Handle("/", &app.Handler{Name: "Hello"})
    http.ListenAndServe(":8080", nil)
}
```

## Introduction
go-app is a Go package that lets developers write frontend web applications entirely in Go. Your code compiles to WebAssembly and runs in the browser, while a thin Go HTTP server handles routing and asset delivery. The result is a progressive web app with offline support, installability, and the full type safety of Go.

## What go-app Does
- Compiles Go application code to WebAssembly for client-side execution
- Provides a declarative, component-based UI model similar to React
- Generates a service worker and manifest for PWA installability and offline caching
- Handles server-side rendering and prerendering for SEO and fast initial loads
- Manages routing, lifecycle events, and state updates within a single Go codebase

## Architecture Overview
go-app works in two modes simultaneously. On the server side, a Go HTTP handler serves the compiled WASM binary, static assets, and an auto-generated HTML shell. On the client side, the WASM binary bootstraps the component tree, mounts it to the DOM, and handles all user interaction. Components follow a lifecycle pattern with OnMount, OnNav, and Render methods. The framework manages a virtual DOM diffing layer that updates only the changed elements.

## Self-Hosting & Configuration
- Add go-app to your module with `go get github.com/maxence-charriere/go-app/v10`
- Build the client WASM binary with `GOARCH=wasm GOOS=js go build -o web/app.wasm`
- Serve assets via the built-in app.Handler in any Go HTTP server
- Configure the PWA manifest (name, icons, theme color) through app.Handler fields
- Deploy as a single binary plus the WASM file to any hosting provider

## Key Features
- Write frontend and backend in the same language with shared types and logic
- Automatic PWA features including service worker generation and offline caching
- SEO-friendly with server-side and prerendering support out of the box
- No JavaScript, TypeScript, or Node.js tooling required in the build pipeline
- Component-based architecture with lifecycle hooks and event handling

## Comparison with Similar Tools
- **Wails** compiles Go for native desktop apps; go-app targets the browser via WebAssembly
- **Vecty** is another Go-to-WASM framework but lacks built-in PWA and SSR support
- **Lorca** uses Chrome as a UI shell; go-app runs entirely in the browser without requiring Chrome
- **React/Next.js** requires JavaScript and Node.js; go-app keeps everything in Go
- **Fyne** builds native desktop UIs with Go; go-app delivers web UIs through the browser

## FAQ
**Q: How large is the resulting WASM binary?**
A: A minimal go-app binary starts around 5-8 MB. Using TinyGo or wasm-opt can reduce this. Gzip compression brings the transfer size to roughly 1-2 MB.

**Q: Can I use existing JavaScript libraries?**
A: Yes. go-app provides js.Value interop to call JavaScript functions and access browser APIs from Go code.

**Q: Does go-app support hot reloading during development?**
A: Not natively, but you can use tools like air or entr to watch for file changes and rebuild the WASM binary automatically.

**Q: Is go-app suitable for large applications?**
A: go-app scales well for medium-complexity apps. For very large SPAs, the WASM binary size and Go's garbage collector pauses in WASM are factors to evaluate.

## Sources
- https://github.com/maxence-charriere/go-app
- https://go-app.dev

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Source: https://tokrepo.com/en/workflows/asset-6460e985
Author: AI Open Source