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# Go Vanity Import + Git Server Architecture
This document describes a **simple, robust architecture** for hosting Go module source code and enabling `go get` on a **custom domain**, using:
* A basic Git server (authoritative source)
* Go vanity imports
* Caddy for HTTPS with automatic TLS
The design prioritizes:
* Simplicity
* Long-term correctness
* Zero client-side configuration
* Easy future migration to a module proxy if needed
---
## Goals
* Host all authored Go modules under a single domain (e.g. `yourdomain.com/foo`)
* Allow anyone to run:
```bash
go get yourdomain.com/foo
```
with no environment variables or flags
* Retain full control of source code and hosting
* Avoid unnecessary complexity (S3 proxies, CI artifact pipelines) for a single author
---
## High-Level Architecture
```
yourdomain.com
├─ /<module> → Vanity import discovery (?go-get=1)
├─ /<module>.git → Git repository (HTTPS, read-only)
└─ ssh://git@yourdomain.com/<module>.git → Git writes (SSH)
```
Components:
* **Caddy**: Fronts everything, provides HTTPS automatically
* **Vanity Import Server**: Tiny Go HTTP server that serves `<meta go-import>` tags
* **Git Server**: Bare Git repositories served over HTTPS and SSH
---
## How `go get` Works in This Setup
When a user runs:
```bash
go get yourdomain.com/foo
```
Go performs the following steps:
1. **Vanity discovery**
```
GET https://yourdomain.com/foo?go-get=1
```
2. **Vanity server responds** with:
```html
<meta name="go-import"
content="yourdomain.com/foo git https://yourdomain.com/foo.git">
```
3. **Go clones the repository**:
```
git clone https://yourdomain.com/foo.git
```
4. **Go reads `go.mod`**, checks tags (e.g. `v1.2.3`), and builds the module
No Go module proxy is involved.
---
## Module Requirements
Each module repository **must**:
* Be located at `/srv/git/<module>.git`
* Have a `go.mod` file with:
```go
module yourdomain.com/<module>
```
* Use semantic version tags:
```
v1.0.0
v1.2.3
```
Tags must not be rewritten after publication.
---
## Vanity Import Server
A single Go HTTP server can serve vanity imports for **all modules**.
### Responsibilities
* Respond only to `?go-get=1` requests
* Dynamically map paths to Git repositories
* Serve static HTML with `<meta name="go-import">`
### Behavior
For a request to:
```
/foo?go-get=1
```
The server returns:
```html
<meta name="go-import"
content="yourdomain.com/foo git https://yourdomain.com/foo.git">
```
All non-`go-get` requests return `404` (or are handled elsewhere).
---
## Git Server
### Repository Layout
```
/srv/git/
├─ foo.git
├─ bar.git
└─ baz.git
```
Repositories are:
* **Bare**
* Read-only over HTTPS
* Writable only via SSH
### Write Access
* SSH only
* Single `git` user
* Access controlled via `authorized_keys`
Example push:
```bash
git push git@yourdomain.com:/srv/git/foo.git
```
---
## Caddy Configuration
Caddy is used as the front-facing server.
### Responsibilities
* Automatic HTTPS (Let’s Encrypt)
* Route `.git` paths to `git-http-backend`
* Route all other paths to the vanity import server
### Conceptual Routing
* `/*.git*` → Git HTTP backend
* `/*` → Vanity import server
This keeps TLS, routing, and process management simple and centralized.
---
## Why This Design Is “Bullet-Proof Simple”
### Advantages
* No module proxy implementation required
* No S3, CloudFront, or artifact format rules
* No CI publishing pipeline needed
* Fully compatible with Go tooling
* Easy to debug (if `git clone` works, `go get` works)
* Mirrors Go’s original and still-supported design
### Trade-offs
* Git-based fetching is slower than a proxy
* No immutable release guarantees beyond Git tags
* Less suitable for very high traffic
For a single-author, self-hosted setup, these trade-offs are acceptable.
---
## Future Migration Path (Optional)
If needed later, this setup can evolve into a module proxy:
* Keep vanity import paths unchanged
* Switch `<meta go-import>` from `git` → `mod`
* Introduce an S3-backed module proxy
* Users do not need to change imports or commands
This design does not lock you into Git forever.
---
## Summary
This architecture provides:
* A single, authoritative domain for all Go modules
* Simple Git-based source hosting
* Zero-config `go get` for users
* Minimal operational complexity
* A clean upgrade path to a full module proxy
It is the simplest solution that is still fully correct and future-proof for Go modules.
|
