gin-oauth2 puts OAuth2 authorisation on a Gin router group

Written because the Gin and OAuth2 worlds did not meet

gin-oauth2 is described as specially made for Gin Framework users who also want to use OAuth2, and the origin story is in the README: it was created by Go developers who needed Gin middleware for working with OAuth2 and could not find any. That gap between two mature ecosystems is the whole reason the package exists, and it explains the shape of the API. The project context section is candid about Go framework fragmentation, notes that detailed comparisons between frameworks are still somewhat rare, and says the authors liked Gin for its speed, accessibility and usefulness in microservice architectures. Their goal in building the package was to take fuller advantage of Gin's capabilities and to help other developers do the same. The result is a middleware layer rather than a framework, which is the right size for the problem and also the right size for review.

Access tuples are the access control unit

The unit of authorisation is an access triple, and it has three fields. The first is a namespace, and the project suggests values like employees or services, the second is a Unix name, and the third is the real name of the person. Users are declared as a slice of these tuples, and a checker function is handed that slice when the route group is set up. The declared shape of the struct is worth reading, because it tells you what the middleware expects your identity provider to hand back.

        // from zalando package
        // type AccessTuple struct {
        //      Realm string // p.e. "employees", "services"
        //      Uid   string // UnixName
        //      Cn    string // RealName
        // }
        var USERS []zalando.AccessTuple = []zalando.AccessTuple{
	    {"/employees", "sszuecs", "Sandor Szücs"},
            {"/employees", "njuettner", "Nick Jüttner"},
        }

A router group carries the authorisation

The middleware sits on a Gin router group, which is what makes it easy to read. The first group of the example is a private area for one user, and the group line is where the check and the token endpoint are supplied.

	privateUser := router.Group("/api/privateUser")
	privateUser.Use(ginoauth2.Auth(zalando.UidCheck(USERS), zalando.OAuth2Endpoint))
	privateUser.GET("/", func(c *gin.Context) {

The handler then pulls the real name out of the context with c.Get("cn"), which works because the middleware has already established who the caller is. Two lines of middleware cover the whole stack, with the request logger in between.

	router := gin.New()
	router.Use(ginglog.Logger(3 * time.Second))
	router.Use(ginoauth2.RequestLogger([]string{"uid"}, "data"))
	router.Use(gin.Recovery())

Teams use the same model with a different check

Team based access follows the same three steps with a different checker and a different namespace value, and the tuple list is the only part that changes. The handler then reads two values from the context, the uid and the team, and reports both. The important detail for an integrator is that the middleware puts identity information into the Gin context under the keys uid, cn and team, which is how a handler learns who is calling it. That is the whole contract between the middleware and your code: the check happens once at the group, and the handler reads claims that are already known to be authorised.

Running the example and getting a token

The repository ships three example services, one per identity source, and the zalando one is the fullest. The install itself is a single command.

    go get github.com/zalando/gin-oauth2

The service is then started with the standard Go tool, and the flags in the command are the interesting part, because they turn on verbose logging to standard error.

    % go run example/zalando/main.go -v=2 -logtostderr
    [GIN-debug] [WARNING] Running in "debug" mode. Switch to "release" mode in production.

A token comes from your own provider, and the example shows that as a plain curl against a token URL, with the credentials in the URL.

    % TOKEN=$(curl https://$USER:[email protected]/access_token)

The request then carries it as a bearer token, and the response shows the uid and the team that the middleware resolved.

    % curl -H "Authorization: Bearer $TOKEN" http://localhost:8081/api/privateGroup/
    {"message":"Hello from private to sszuecs member of teapot"}

The example service listens on port 8081, and the startup log shows the access tuples being registered.

Request logging and the middleware stack

The example shows a three line middleware stack, and the middle line is the one specific to this package. The logger records how long the request took, the method and the path, and the request logger from the package adds a line for every request that carries the listed context values, here uid and data, so an audit trail is a config change rather than an addition to every handler. The recovery middleware at the end catches panics. The order matters in the way it matters everywhere in Gin, with the request logger placed so that it sees the values the OAuth2 middleware has already put into the context, and that ordering is the kind of thing worth getting right once rather than debugging later. The package depends on Gin, on glog and on gin-glog, so logging is a first class concern here rather than an afterthought.

Zalando, GitHub and Google in one repository

The top level of the repository shows how much this is an integration package. There is a zalando directory for the uid and team based checks used above, a github directory and a google directory for the same job with different providers, a ginoauth2.go file with the core middleware, a logging.go file, an example directory with the three sample services, a doc directory and a github directory at the top level that appears to hold the provider specific integration. The README points at an article on Google sign in with Go, and there is a Google based access section that follows the same shape as the other two. The requirements list is short and worth reading as a deployment checklist: Gin, an OAuth2 token provider, which the project recommends you run yourself, dex being the example, and a tokeninfo service, dex again being the example. In other words the package deliberately does not bundle an identity provider, it talks to one you already have.

MIT licensed, actively patched, and open about who maintains it

The licence is MIT, and the release record shows a steady stream of patch releases: v1.5.16 on 2026-05-05, v1.5.17 on 2026-06-25 and v1.5.18 on 2026-09-08, with the last push on 2026-10-20. The project is maintained by a group rather than a single person, with a MAINTAINERS file, a SECURITY policy, a contributing guide and a Zappr configuration for pull request approvals, and it also carries a catwatch configuration for the dependency update bot. The README points new users to two background resources, OAuth 2 Simplified and an introduction to OAuth 2, which is a sensible thing for a package whose users are often new to the protocol as well as to the framework.

Editorial conclusion

gin-oauth2 suits a Go team that has already chosen Gin, runs its own OAuth2 provider, and wants authorisation attached to a route group instead of scattered through handlers. It does not suit a service that expects a hosted identity provider, because the project asks you to bring your own token provider and tokeninfo service, and it does not cover authorisation policy beyond uid and team checks, since the README says you write your own authorization functions. Before you adopt it, run the zalando example locally, get a token from your provider, and confirm the uid and team claims your provider issues match the access tuples you plan to define.

Frequently asked questions

Official sources

1. Issues
2. License: MIT
3. README
4. Releases
5. zalando/gin-oauth2 on GitHub