Go SDK for server-side tag management — receive, enrich, and forward Google Analytics 4 traffic on your own infrastructure.

sesamy-go lets you run a first-party tagging endpoint in Go. It accepts inbound GA4 traffic in both protocols GA4 uses — GTag (the form-encoded protocol used by gtag.js) and Measurement Protocol v2 (JSON) — runs your enrichment and validation middleware, then forwards events to a downstream tagging server (sGTM, GA4, BigQuery, vendor endpoints).

It pairs with foomo/sesamy-cli, which generates the GTM container that points gtag.js at your sesamy-go endpoint and emits matching Go event types.

• GTag + MPv2 — decode, encode, and round-trip between both wire formats.
• Composable middleware — client ID, session ID, user ID, IP override, page location, engagement time, user-agent, debug mode, timeouts, logging, OpenTelemetry trace correlation.
• Typed events — generic Event[P] with 44 predefined GA4 event names and your own param structs.
• Direct client — emit events server-to-GA without going through a browser (client.MPv2, client.GTag).
• Providers — Cookiebot consent, Emarsys marketing events, Tracify attribution.
• Grafana Loki integration — ship events via protobuf + snappy with batched delivery and backoff retry.
• Bring your own router — exposes http.HandlerFunc values; no framework lock-in.

go get github.com/foomo/sesamy-go

package main

import (
  "log"
  "net/http"

  "github.com/foomo/sesamy-go/pkg/collect"
  "go.uber.org/zap"
)

func main() {
  l, _ := zap.NewProduction()

  c, err := collect.New(l,
    collect.WithTagging("https://sgtm.example.com"),
  )
  if err != nil {
    log.Fatal(err)
  }

  mux := http.NewServeMux()
  mux.HandleFunc("/g/collect", c.GTagHTTPHandler)  // gtag.js
  mux.HandleFunc("/mp/collect", c.MPv2HTTPHandler) // Measurement Protocol v2

  log.Fatal(http.ListenAndServe(":8080", mux))
}

Point gtag.js at https://your-domain/g/collect (via the GTM container generated by sesamy-cli) and events flow through your middleware to the configured tagging server.

• Docs site — https://foomo.github.io/sesamy-go/
• API reference — https://pkg.go.dev/github.com/foomo/sesamy-go
• Companion CLI — https://github.com/foomo/sesamy-cli

Start at the Getting Started guide and the core concepts page.

make check        # tidy + generate + lint + test
make test         # tests with -tags=safe
make test.race    # tests with race detector
make lint.fix     # auto-fix lint

Requires mise for tool management (mise install).

• GA4 event naming rules
• GA4 Measurement Protocol v2
• GA4 reserved names and parameters

Contributions are welcome! Please read the contributing guide.

Distributed under MIT License, please see the license file within the code for more details.

Made with ♥ foomo by bestbytes