fixes issue 375: context not preserved after routing

After RouteInfo is called new request object with new context is passed,
and all middlewares handling that request after returning don't have
access to it. This fix copies the request with routing context to the
request passed as a function variable so all middlewares now preserve
the request context.

Author: mjuraga

middleware/router.go

@@ -65,6 +65,7 @@ func NewRouter(ctx *Context, next http.Handler) http.Handler {
 	return http.HandlerFunc(func(rw http.ResponseWriter, r *http.Request) {
 		if _, rCtx, ok := ctx.RouteInfo(r); ok {
 			next.ServeHTTP(rw, rCtx)
+			*r = *rCtx
 			return
 		}
 

middleware/router_context_test.go

@@ -0,0 +1,65 @@
+package middleware
+
+import (
+	stdcontext "context"
+	stderrors "errors"
+	"fmt"
+	"io"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	"github.com/go-openapi/runtime/internal/testing/petstore"
+	"github.com/go-openapi/testify/v2/assert"
+	"github.com/go-openapi/testify/v2/require"
+)
+
+func TestRouterContext_Issue375(t *testing.T) {
+	spec, api := petstore.NewAPI(t)
+	spec.Spec().BasePath = "/api/"
+	context := NewContext(spec, api, nil)
+
+	type authCtxKey uint8
+	const authCtx authCtxKey = iota + 1
+	authCtxErr := stderrors.New("test error in context")
+
+	mw := NewRouter(context, http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		// check context after API middleware
+		authContext := stdcontext.WithValue(r.Context(), authCtx, authCtxErr)
+		*r = *r.WithContext(authContext)
+	}))
+
+	start := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		t.Logf("calling API router with context: %v", authCtxErr)
+		mw.ServeHTTP(w, r)
+
+		value := r.Context().Value(authCtx)
+		assert.NotNilf(t, value, "end of middleware chain: expected to find authCtx in request context")
+
+		if value == nil {
+			w.WriteHeader(http.StatusInternalServerError)
+		}
+
+		errAuth, ok := value.(error)
+		assert.Truef(t, ok, "expected authCtx to be an error, but got: %T", value)
+		t.Logf("got context from request: %v", errAuth)
+		fmt.Fprintf(w, "%v", errAuth)
+		w.WriteHeader(http.StatusOK)
+
+		// *r = *r.WithContext(authContext)
+		// mw.ServeHTTP(w, r)
+	})
+
+	recorder := httptest.NewRecorder()
+	request, err := http.NewRequestWithContext(stdcontext.Background(), http.MethodGet, "/api/pets/123", nil)
+	require.NoError(t, err)
+
+	start.ServeHTTP(recorder, request)
+	assert.Equal(t, http.StatusOK, recorder.Code)
+
+	res := recorder.Result()
+	require.NotNil(t, res.Body)
+	msg, err := io.ReadAll(res.Body)
+	require.NoError(t, err)
+	t.Logf("response message: %q", string(msg))
+}