Introduction

Forst is a programming language that helps you move TypeScript backends to Golang. To accomplish this, it supports you in four key ways:

Benefit	How it works
Go ecosystem	Compiles directly to Go. You get full access to the Go package ecosystem, standard library and build tools.
TypeScript integration	Generates native TS definitions and a client directly from your backend source. No need for intermediate languages like GraphQL or Protobuf just for type safety.
Node.js interop	Call existing Node.js code directly from Forst to keep your existing tools and libraries during migration.
Incremental migration	Allows you to move small parts of your code at a time while your existing codebase keeps running, so you can keep shipping during migration.

Why?

Building backend APIs often forces a trade off between runtime performance and developer speed. Maintaining separate schema contracts leads to lots of glue code. Full backend rewrites into more performant languages are often impossible to do safely. Forst exists to remove that friction. You can migrate incrementally or write completely new backends with native performance and an ergonomic DX by design.

Validation and errors

Type constraints validate incoming data automatically before it reaches your application logic. Constraints on the type replace manual checks at the boundary:

Forst
Generated Go
Generated TypeScript

type PlaceOrderInput = {
	stockKeepingUnit: String.Min(1).Max(64),
	quantity:         Int.Min(1).Max(99),
}

func placeOrder(in PlaceOrderInput) {
	// in is already validated; business logic starts here
}

// forst build
type PlaceOrderInput struct {
	stockKeepingUnit string
	quantity         int
}

func placeOrder(in PlaceOrderInput) {
	if len(in.stockKeepingUnit) < 1 || len(in.stockKeepingUnit) > 64 { ... }
	if in.quantity < 1 || in.quantity > 99 { ... }
	// business logic starts here
}

// forst generate → @forst/gen
export interface PlaceOrderInput {
  quantity: number;
  stockKeepingUnit: string;
}

Forst is actively developed. Some features are experimental. See the roadmap for current status.

How it fits your stack

Forst compiles .ft sources to Go, and optionally emits TypeScript types for clients: Run forst generate when clients need TypeScript from the same source.

Start here

Why Forst?

Design priorities and what Forst omits.

Quickstart

Install, write your first .ft file, and run it.

Language overview

Go alignment, structural typing, and explicit control flow.

Validated shapes

Types as schemas with built in constraints.

Mix with Go packages

Import Go packages and mix .ft with .go.

Examples and packages

Compiler examples: github.com/forst-lang/forst/tree/main/examples/in
npm compiler: @forst/cli
Gradual adoption: @forst/sidecar for invoking Forst from Node during migration

For client type generation, see Generate client types.

Overview

Getting started

Data validation

Behavior

Interoperability

Workflow

Introduction

Why?

Validation and errors

How it fits your stack

Start here

Why Forst?

Quickstart

Language overview

Validated shapes

Mix with Go packages

Examples and packages

​Why?

​Validation and errors

​How it fits your stack

​Start here

Why Forst?

Quickstart

Language overview

Validated shapes

Mix with Go packages

​Examples and packages

Why?

Validation and errors

How it fits your stack

Start here

Examples and packages