G0 CMS

A lightweight, single-binary content management system. Because 25MB is enough.

Philosophy

G0 CMS is built on a simple premise: modern CMS solutions are bloated.

WordPress requires PHP, MySQL, and prayer. Ghost needs Node.js and 500MB of npm packages. Even "lightweight" solutions demand Docker orchestration.

G0 rejects this. One binary. One config file. One database. Done.

Features

• Single Binary - Everything embedded at compile time (~27MB)
• Zero Dependencies - No PHP, no Node.js, no containers required
• SQLite or PostgreSQL - SQLite for simplicity, Postgres for scale
• Google OAuth - Secure admin access, no password management
• Setup Wizard - First-run configuration UI, no manual config editing
• SEO Built-in - Sitemap, Atom feed, Open Graph tags
• Dark/Light Theme - User preference respected
• Markdown + HTML - Write content your way

Quick Start

# Download the binary (or build from source)
./g0

# Visit http://localhost:8080
# Complete the setup wizard
# Start creating content

Building from Source

git clone https://github.com/hugopalma17/g0
cd g0
go build -o g0 .
./g0

Requires Go 1.22+

Google OAuth Setup

G0 uses Google OAuth for admin authentication. You need to create your own credentials:

Step 1: Create a Google Cloud Project

1. Go to Google Cloud Console
2. Create a new project (or select existing)
3. Note your project name

Step 2: Configure OAuth Consent Screen

1. Navigate to APIs & Services → OAuth consent screen
2. Select External (unless you have Google Workspace)
3. Fill in required fields:
   • App name: Your Site Name
   • User support email: your@email.com
   • Developer contact: your@email.com
4. Click Save and Continue
5. Skip Scopes (we only need basic profile)
6. Add your email as a Test user (required while in testing mode)
7. Save

Step 3: Create OAuth Credentials

1. Navigate to APIs & Services → Credentials
2. Click + CREATE CREDENTIALS → OAuth client ID
3. Application type: Web application
4. Name: G0 CMS
5. Authorized redirect URIs - Add your callback URL:

   https://yourdomain.com/api/auth/callback
   

   For local development:

   http://localhost:8080/api/auth/callback
   

6. Click Create
7. Copy your Client ID and Client Secret

Step 4: Enter Credentials in Setup Wizard

When you run G0 for the first time, enter:

• Admin Email: Must match a Google account (the one you added as test user)
• Client ID: xxxx.apps.googleusercontent.com
• Client Secret: GOCSPX-xxxx

Important: Your redirect URI in Google Console must exactly match your site URL + /api/auth/callback

Publishing Your App (Optional)

While in "Testing" mode, only emails you've added as test users can log in. To allow any email in your allowed_emails config:

1. Go to OAuth consent screen
2. Click PUBLISH APP
3. Complete verification if required (for public apps)

For personal/private sites, keeping it in Testing mode and adding your email as a test user is sufficient.

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Configuration

On first run, G0 presents a setup wizard. All persistent data is stored in ./data/:

data/
├── config.yaml    # Configuration (created by wizard)
└── g0.db          # SQLite database

Configuration example (data/config.yaml):

site:
  name: "My Site"
  url: "https://example.com"
  tagline: "A site built with G0"
  author: "Your Name"

database:
  driver: "sqlite"      # or "postgres"
  path: "./data/g0.db"  # SQLite path

auth:
  provider: "google"
  client_id: "xxx.apps.googleusercontent.com"
  client_secret: "xxx"
  redirect_url: "https://example.com/api/auth/callback"
  allowed_emails:
    - "admin@example.com"
  session_key: ""    # Auto-generated if empty

server:
  host: "0.0.0.0"
  port: "8080"
  admin_path: "/admin"                  # Custom admin URL

Routes

Route	Description
/	Homepage
/journal	Blog listing
/journal/{slug}	Blog post
/resume	Resume page
/contact	Contact form
/admin (customizable)	Admin panel (OAuth protected)
/sitemap.xml	Dynamic sitemap
/feed.atom	Atom feed

Admin Panel

Access your admin panel (default /admin, customizable in setup) to:

• Create/edit/delete content
• Manage blog posts, pages, and sections
• Edit SEO metadata
• Access database manager
• Use built-in terminal (for server access)

Content Types

Type	Purpose
blog	Journal/blog entries
home	Homepage content
resume	Resume page
contact	Contact page content

Deployment

Option 1: Direct Binary

./g0
# Runs on :8080 by default

Option 2: Systemd Service

[Unit]
Description=G0 CMS
After=network.target

[Service]
Type=simple
User=www-data
WorkingDirectory=/opt/g0
ExecStart=/opt/g0/g0
Restart=always

[Install]
WantedBy=multi-user.target

Option 3: Docker

docker build -t g0 .
docker run -p 8080:8080 -v $(pwd)/data:/app/data g0

Reverse Proxy (Caddy)

example.com {
    reverse_proxy localhost:8080
}

Stack

Layer	Technology
Language	Go
Database	SQLite / PostgreSQL
Templates	Go html/template
Interactivity	htmx + Vanilla JS
Styling	Tailwind (compiled)
Auth	Google OAuth OIDC

Development Status

Completed

• Core CMS functionality
• Setup wizard
• SQLite/PostgreSQL support
• Google OAuth admin
• SEO (sitemap, feeds, OG tags)
• Dark/light theme

In Progress

• Admin panel editor rewrite (proper WYSIWYG + iframe preview)
• Theme system (runtime theme loading)
• Plugin architecture

Planned

• Image upload/management
• Multiple admin users
• Content versioning
• One-click deploy templates

Project Structure

g0/
├── internal/
│   ├── auth/         # OAuth + session auth
│   ├── handlers/     # HTTP routes + handlers
│   ├── middleware/   # Host/track placeholders
│   ├── services/     # DB + services
│   └── utils/        # Helpers
├── main.go           # Core server
├── config.yaml       # Runtime config (created by wizard)
├── go.mod
├── go.sum
├── static/
│   ├── css/          # Stylesheets
│   ├── js/           # JavaScript
│   ├── fonts/        # Web fonts
│   └── images/       # Static images
├── templates/
│   ├── admin.html          # Admin panel
│   └── themes/
│       └── default/
│           ├── index.html  # Base layout
│           ├── home.html   # Homepage
│           ├── journal.html # Blog template
│           ├── resume.html # Resume template
│           ├── contact.html # Contact template
│           ├── 404.html    # Error page
│           └── static/     # Theme assets (css, js, images)
└── data/
    └── g0.db         # SQLite database (runtime)

Template Tutorial (Index + Body)

G0 renders every page through templates/themes/default/index.html, which defines a {{block "content" .}} section. Each page template only needs to define that block.

1. Create a new template, for example templates/themes/default/about.html:

{{define "content"}}
<section class="max-w-4xl">
  <div class="prose max-w-none">
    <h2>About</h2>
    <p>Write your content here.</p>
  </div>
</section>
{{end}}

1. Add a route in internal/handlers/routes.go by copying the home/resume/contact cases and pointing to your new template.
2. Create content in the admin panel with the matching type (for example about).

The base layout, navigation, and footer stay in index.html; your page body lives in its own template.

Custom Page Guide

Use this workflow to add a new page type end-to-end. The base layout lives in templates/themes/default/index.html, and each page only provides the {{define "content"}} block.

1. Create the page body in templates/themes/default/<page>.html:

{{define "content"}}
<section class="max-w-4xl">
  {{if .Content}}
  <div class="prose max-w-none">
    {{.Content}}
  </div>
  {{else}}
  <div class="prose max-w-none">
    <h2>About</h2>
    <p>Write your content here.</p>
  </div>
  {{end}}
</section>
{{end}}

1. Register the route in internal/handlers/routes.go inside the switch view block:

case "about":
    targetTemplate = "templates/themes/default/about.html"
    for i := range entries {
        if entries[i].Type == "about" {
            matchedEntry = &entries[i]
            break
        }
    }

1. Create content in the admin panel with type = about. That content becomes {{.Content}} on the page.

2. If the page should appear in the navigation, add a link in templates/themes/default/index.html.

3. If you want SEO tags for this page, add JSON metadata in the admin panel (Metadata field). The layout reads it and fills {{.SeoDesc}}, {{.SeoImage}}, and {{.SeoKeywords}}.

Template Data You Can Use

• {{.Content}} HTML content for the page
• {{.Title}} page title
• {{.Site.Name}}, {{.Site.Tagline}}, {{.Site.Author}}
• {{.SeoDesc}}, {{.SeoImage}}, {{.SeoKeywords}}
• {{.AdminPath}}, {{.Theme}}, {{.Year}}

SEO Tags (per page)

Add JSON metadata in the admin panel (Metadata field):

{"title": "About | My Site", "description": "Short summary", "og_image": "/static/images/og-image.jpg", "keywords": "about, company"}

How it works:

• The JSON above is stored in the database in the content.metadata column for that page.
• On render, the server parses that JSON and maps it to Title, SeoDesc, SeoImage, and SeoKeywords for the template.
• og:title uses metadata.title if present, otherwise the entry title, otherwise the site name.
• og:description uses metadata.description if present, otherwise site.description from config.yaml.
• og:image uses metadata.og_image if present, otherwise site.url + /static/images/og-image.jpg. Set site.url if you want absolute OG URLs.

Optional auto-generation:

• If you add a metadata generation script such as generatemetadate.js, you must install and configure a provider (Copilot, Gemini, or similar) before running it. This repo does not ship that dependency by default.

Security

• OAuth tokens never stored, session-based auth
• Config file written with 0600 permissions
• Admin JS files protected behind auth
• No directory listing on static files
• SQL injection prevention via parameterized queries

Troubleshooting

"redirect_uri_mismatch" Error

Your callback URL in Google Console doesn't match your site. Ensure:

• Google Console has: https://yourdomain.com/api/auth/callback
• Matches exactly (http vs https, trailing slashes matter)

"Access blocked: App not verified"

Your OAuth app is in testing mode. Either:

1. Add your email as a test user in Google Console
2. Or publish the app (requires verification for public use)

"Unauthorized: Email not allowed"

The Google account you logged in with isn't in the allowed_emails list in config.yaml.

Database Errors on Startup

• SQLite: Ensure the data/ directory is writable
• PostgreSQL: Check connection details and that the database exists

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License

MIT

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G0 CMS: What if your CMS respected your server?