set transport.kind to be strongly typed (#728)

Signed-off-by: storyicon <storyicon@foxmail.com>

transport/grpc/client.go

@@ -101,7 +101,7 @@ func dial(ctx context.Context, insecure bool, opts ...ClientOption) (*grpc.Clien
 // UnaryClientInterceptor retruns a unary client interceptor.
 func UnaryClientInterceptor(m middleware.Middleware) grpc.UnaryClientInterceptor {
 	return func(ctx context.Context, method string, req, reply interface{}, cc *grpc.ClientConn, invoker grpc.UnaryInvoker, opts ...grpc.CallOption) error {
-		ctx = transport.NewContext(ctx, transport.Transport{Kind: "gRPC"})
+		ctx = transport.NewContext(ctx, transport.Transport{Kind: transport.KindGRPC})
 		ctx = NewClientContext(ctx, ClientInfo{FullMethod: method})
 		h := func(ctx context.Context, req interface{}) (interface{}, error) {
 			return reply, invoker(ctx, method, req, reply, cc, opts...)

transport/grpc/server.go

@@ -146,7 +146,7 @@ func UnaryTimeoutInterceptor(timeout time.Duration) grpc.UnaryServerInterceptor
 // UnaryServerInterceptor returns a unary server interceptor.
 func UnaryServerInterceptor(m middleware.Middleware) grpc.UnaryServerInterceptor {
 	return func(ctx context.Context, req interface{}, info *grpc.UnaryServerInfo, handler grpc.UnaryHandler) (interface{}, error) {
-		ctx = transport.NewContext(ctx, transport.Transport{Kind: "gRPC"})
+		ctx = transport.NewContext(ctx, transport.Transport{Kind: transport.KindGRPC})
 		ctx = NewServerContext(ctx, ServerInfo{Server: info.Server, FullMethod: info.FullMethod})
 		h := func(ctx context.Context, req interface{}) (interface{}, error) {
 			return handler(ctx, req)

transport/http/client.go

@@ -90,7 +90,7 @@ func (t *baseTransport) RoundTrip(req *http.Request) (*http.Response, error) {
 	if t.userAgent != "" && req.Header.Get("User-Agent") == "" {
 		req.Header.Set("User-Agent", t.userAgent)
 	}
-	ctx := transport.NewContext(req.Context(), transport.Transport{Kind: "HTTP"})
+	ctx := transport.NewContext(req.Context(), transport.Transport{Kind: transport.KindHTTP})
 	ctx = NewClientContext(ctx, ClientInfo{Request: req})
 	ctx, cancel := context.WithTimeout(ctx, t.timeout)
 	defer cancel()

transport/http/server.go

@@ -96,7 +96,7 @@ func (s *Server) HandleFunc(path string, h http.HandlerFunc) {
 func (s *Server) ServeHTTP(res http.ResponseWriter, req *http.Request) {
 	ctx, cancel := context.WithTimeout(req.Context(), s.timeout)
 	defer cancel()
-	ctx = transport.NewContext(ctx, transport.Transport{Kind: "HTTP"})
+	ctx = transport.NewContext(ctx, transport.Transport{Kind: transport.KindHTTP})
 	ctx = NewServerContext(ctx, ServerInfo{Request: req, Response: res})
 	s.router.ServeHTTP(res, req.WithContext(ctx))
 }

transport/transport.go

@@ -17,9 +17,18 @@ type Server interface {
 
 // Transport is transport context value.
 type Transport struct {
-	Kind string
+	Kind Kind
 }
 
+// Kind defines the type of Transport
+type Kind string
+
+// Defines a set of transport kind
+const (
+	KindGRPC Kind = "gRPC"
+	KindHTTP Kind = "HTTP"
+)
+
 type transportKey struct{}
 
 // NewContext returns a new Context that carries value.