ci: add golangci-lint

.github/workflows/golangci-lint.yml

@@ -0,0 +1,23 @@
+name: golangci-lint
+on:
+  push:
+    branches:
+      - main
+  pull_request:
+
+permissions:
+  contents: read
+
+jobs:
+  golangci:
+    name: lint
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-go@v5
+        with:
+          go-version: stable
+      - name: golangci-lint
+        uses: golangci/golangci-lint-action@v8
+        with:
+          version: v2.1

.golangci.yml

@@ -0,0 +1,6 @@
+version: "2"
+linters:
+  exclusions:
+    presets:
+      - std-error-handling
+

client/transport/streamable_http_test.go

@@ -46,11 +46,14 @@ func startMockStreamableHTTPServer() (string, func()) {
 			w.Header().Set("Mcp-Session-Id", sessionID)
 			w.Header().Set("Content-Type", "application/json")
 			w.WriteHeader(http.StatusAccepted)
-			json.NewEncoder(w).Encode(map[string]any{
+			if err := json.NewEncoder(w).Encode(map[string]any{
 				"jsonrpc": "2.0",
 				"id":      request["id"],
 				"result":  "initialized",
-			})
+			}); err != nil {
+				http.Error(w, "Failed to encode response", http.StatusInternalServerError)
+				return
+			}
 
 		case "debug/echo":
 			// Check session ID
@@ -62,11 +65,14 @@ func startMockStreamableHTTPServer() (string, func()) {
 			// Echo back the request as the response result
 			w.Header().Set("Content-Type", "application/json")
 			w.WriteHeader(http.StatusOK)
-			json.NewEncoder(w).Encode(map[string]any{
+			if err := json.NewEncoder(w).Encode(map[string]any{
 				"jsonrpc": "2.0",
 				"id":      request["id"],
 				"result":  request,
-			})
+			}); err != nil {
+				http.Error(w, "Failed to encode response", http.StatusInternalServerError)
+				return
+			}
 
 		case "debug/echo_notification":
 			// Check session ID
@@ -104,14 +110,17 @@ func startMockStreamableHTTPServer() (string, func()) {
 			w.Header().Set("Content-Type", "application/json")
 			w.WriteHeader(http.StatusOK)
 			data, _ := json.Marshal(request)
-			json.NewEncoder(w).Encode(map[string]any{
+			if err := json.NewEncoder(w).Encode(map[string]any{
 				"jsonrpc": "2.0",
 				"id":      request["id"],
 				"error": map[string]any{
 					"code":    -1,
 					"message": string(data),
 				},
-			})
+			}); err != nil {
+				http.Error(w, "Failed to encode response", http.StatusInternalServerError)
+				return
+			}
 		}
 	})
 

examples/custom_context/main.go

@@ -125,7 +125,7 @@ func NewMCPServer() *MCPServer {
 func (s *MCPServer) ServeSSE(addr string) *server.SSEServer {
 	return server.NewSSEServer(s.server,
 		server.WithBaseURL(fmt.Sprintf("http://%s", addr)),
-		server.WithSSEContextFunc(authFromRequest),
+		server.WithHTTPContextFunc(authFromRequest),
 	)
 }
 

examples/everything/main.go

@@ -392,7 +392,7 @@ func handleLongRunningOperationTool(
 	for i := 1; i < int(steps)+1; i++ {
 		time.Sleep(time.Duration(stepDuration * float64(time.Second)))
 		if progressToken != nil {
-			server.SendNotificationToClient(
+			err := server.SendNotificationToClient(
 				ctx,
 				"notifications/progress",
 				map[string]any{
@@ -402,6 +402,9 @@ func handleLongRunningOperationTool(
 					"message":       fmt.Sprintf("Server progress %v%%", int(float64(i)*100/steps)),
 				},
 			)
+			if err != nil {
+				return nil, fmt.Errorf("failed to send notification: %w", err)
+			}
 		}
 	}
 

mcp/types.go

@@ -67,7 +67,7 @@ type URITemplate struct {
 }
 
 func (t *URITemplate) MarshalJSON() ([]byte, error) {
-	return json.Marshal(t.Template.Raw())
+	return json.Marshal(t.Raw())
 }
 
 func (t *URITemplate) UnmarshalJSON(data []byte) error {

server/server_test.go

@@ -368,7 +368,7 @@ func TestMCPServer_Tools(t *testing.T) {
 				"id": 1,
 				"method": "tools/list"
 			}`))
-			tt.validate(t, notifications, toolsList.(mcp.JSONRPCMessage))
+			tt.validate(t, notifications, toolsList)
 		})
 	}
 }

server/session_test.go

@@ -573,7 +573,8 @@ func TestMCPServer_NotificationChannelBlocked(t *testing.T) {
 	require.NoError(t, err)
 
 	// Fill the buffer first to ensure it gets blocked
-	server.SendNotificationToSpecificClient(session.SessionID(), "first-message", nil)
+	err = server.SendNotificationToSpecificClient(session.SessionID(), "first-message", nil)
+	require.NoError(t, err)
 
 	// This will cause the buffer to block
 	err = server.SendNotificationToSpecificClient(session.SessionID(), "blocked-message", nil)

server/sse.go

@@ -185,7 +185,7 @@ func WithSSEEndpoint(endpoint string) SSEOption {
 // WithSSEContextFunc sets a function that will be called to customise the context
 // to the server using the incoming request.
 //
-// Deprecated: Use WithContextFunc instead. This will be removed in a future version.
+// Deprecated: Use WithHTTPContextFunc instead. This will be removed in a future version.
 //
 //go:deprecated
 func WithSSEContextFunc(fn SSEContextFunc) SSEOption {
@@ -297,7 +297,11 @@ func (s *SSEServer) handleSSE(w http.ResponseWriter, r *http.Request) {
 	defer s.sessions.Delete(sessionID)
 
 	if err := s.server.RegisterSession(r.Context(), session); err != nil {
-		http.Error(w, fmt.Sprintf("Session registration failed: %v", err), http.StatusInternalServerError)
+		http.Error(
+			w,
+			fmt.Sprintf("Session registration failed: %v", err),
+			http.StatusInternalServerError,
+		)
 		return
 	}
 	defer s.server.UnregisterSession(r.Context(), sessionID)
@@ -480,7 +484,14 @@ func (s *SSEServer) writeJSONRPCError(
 	response := createErrorResponse(id, code, message)
 	w.Header().Set("Content-Type", "application/json")
 	w.WriteHeader(http.StatusBadRequest)
-	json.NewEncoder(w).Encode(response)
+	if err := json.NewEncoder(w).Encode(response); err != nil {
+		http.Error(
+			w,
+			fmt.Sprintf("Failed to encode response: %v", err),
+			http.StatusInternalServerError,
+		)
+		return
+	}
 }
 
 // SendEventToSession sends an event to a specific SSE session identified by sessionID.
@@ -621,7 +632,11 @@ func (s *SSEServer) MessageHandler() http.Handler {
 // ServeHTTP implements the http.Handler interface.
 func (s *SSEServer) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	if s.dynamicBasePathFunc != nil {
-		http.Error(w, (&ErrDynamicPathConfig{Method: "ServeHTTP"}).Error(), http.StatusInternalServerError)
+		http.Error(
+			w,
+			(&ErrDynamicPathConfig{Method: "ServeHTTP"}).Error(),
+			http.StatusInternalServerError,
+		)
 		return
 	}
 	path := r.URL.Path

server/sse_test.go

@@ -29,6 +29,7 @@ func TestSSEServer(t *testing.T) {
 
 		if sseServer == nil {
 			t.Error("SSEServer should not be nil")
+			return
 		}
 		if sseServer.server == nil {
 			t.Error("MCPServer should not be nil")
@@ -1247,7 +1248,7 @@ func TestSSEServer(t *testing.T) {
 			WithHooks(&Hooks{
 				OnAfterInitialize: []OnAfterInitializeFunc{
 					func(ctx context.Context, id any, message *mcp.InitializeRequest, result *mcp.InitializeResult) {
-						result.Result.Meta = map[string]any{"invalid": func() {}} // marshal will fail
+						result.Meta = map[string]any{"invalid": func() {}} // marshal will fail
 					},
 				},
 			}),