Getting Started¶

Prerequisites¶

Go 1.25 or later
A web browser

Clone and run¶

git clone https://github.com/alimasry/go-collab-editor.git
cd go-collab-editor
go run main.go

The server starts on http://localhost:8080.

To use a custom port:

go run main.go -addr :3000

Try collaboration¶

Open http://localhost:8080 in your browser
Note the URL hash (e.g. #abc123) — this identifies the document
Open the same URL in a second browser tab
Type in both tabs and watch edits appear in real-time

Share the URL with others to collaborate on the same document.

Run tests¶

# Run all tests
go test ./...

# Run a specific package
go test -v ./ot

# Run a single test
go test -v ./ot -run TestTransform_InsertDelete

Project structure¶

Directory	Purpose
`ot/`	Pure OT algorithm library (zero external dependencies)
`server/`	HTTP handler, WebSocket hub, sessions, and client management
`store/`	Document persistence (`MemoryStore`, `FirestoreStore`, and `CachedStore` implementations)
`static/`	Frontend: HTML, CSS, and JavaScript (CodeMirror 5)
`main.go`	Server entry point — wires everything together

Deploy to Cloud Run¶

Build and deploy with Firestore as the storage backend:

# Build the container image
docker build -t go-collab-editor .

# Run locally with Firestore
docker run -p 8080:8080 \
  -e GCP_PROJECT=your-project-id \
  go-collab-editor -store firestore

# Deploy to Cloud Run
gcloud run deploy go-collab-editor \
  --source . \
  --set-env-vars GCP_PROJECT=your-project-id \
  --args="-store=firestore"

The server reads the PORT environment variable automatically (set by Cloud Run).

Storage backends¶

Flag	Description
`-store memory`	In-memory (default) — data lost on restart
`-store firestore`	Google Cloud Firestore with write-behind cache — persistent across restarts

When using Firestore, set the project ID via -project flag or GCP_PROJECT env var.