Context

How to use Context in Tupã

You can access the request context from the Context property within the Tupa struct.

Context in Middlewares

We can easily add context to a request. In Tupã, there are various ways to work with context through the TupaContext. For example, you can set a new context with the SetContext() method, which will attach the context to the request. To obtain the context value, you can use the GetCtx() and CtxValue(ctx) methods.

1. GetCtx(): returns the entire request context.
2. CtxValue(ctx): returns the specific context value according to the specified key.

Let’s add a Context in the MiddlewareSampleRoute() middleware. Note that route-specific middlewares are called first, followed by global middlewares.

func main() {
  server := tupa.NewAPIServer(":6969", exampleManager)
  server.New()
}

func exampleManager() {
  tupa.AddRoutes(tupa.MiddlewareChain{MiddlewareSampleCats}, SampleRouteManager)
}

func MiddlewareSampleCats(next tupa.APIFunc) tupa.APIFunc {
  return func(tc *tupa.TupaContext) error {
    return next(tc)
  }
}

func MiddlewareSampleRoute(next tupa.APIFunc) tupa.APIFunc {
  return func(tc *tupa.TupaContext) error {
    catsCtxKey := "ctxcats"
    ctxMsg := "context of someone interested in cats"
    newCtx := context.WithValue(tc.GetCtx(), catsCtxKey, ctxMsg)
    tc.SetContext(newCtx)

    return next(tc)
  }
}

func SampleRouteManager() []tupa.RouteInfo {
  return []tupa.RouteInfo{
    {
      Path:   "/cats",
      Method: "GET",
      Handler: func(tc *tupa.TupaContext) error {
        ctxFull := tc.GetCtx()
        fmt.Println(ctxFull)

        ctxValue := tc.CtxValue("ctxcats").(string)
        fmt.Println(ctxValue)

        ctxVal := tc.GetCtx().Value("ctxcats").(string)
        fmt.Println(ctxVal)

        resp, err := http.Get("https://cdn2.thecatapi.com/images/dN6eoeLjY.jpg")
        if err != nil {
          return err
        }
        defer resp.Body.Close()
        _, err = io.Copy(*tc.Response(), resp.Body)
        return err
      },
      Middlewares: []tupa.MiddlewareFunc{MiddlewareSampleRoute},
    },
  }
}

Output:

context.Background.WithValue(type *http.contextKey, val <not Stringer>).WithValue(type *http.contextKey, val [::1]:6969).WithCancel.WithCancel.WithValue(type mux.contextKey, val <not Stringer>).WithValue(type mux.contextKey, val <not Stringer>).WithValue(type string, val context of someone interested in cats)
context of someone interested in cats
context of someone interested in cats