[chore][client] Add ability to override the http.Client

Author: sks

client/sse.go

@@ -2,14 +2,20 @@ package client
 
 import (
 	"fmt"
-	"github.com/mark3labs/mcp-go/client/transport"
+	"net/http"
 	"net/url"
+
+	"github.com/mark3labs/mcp-go/client/transport"
 )
 
 func WithHeaders(headers map[string]string) transport.ClientOption {
 	return transport.WithHeaders(headers)
 }
 
+func WithHTTPClient(httpClient *http.Client) transport.ClientOption {
+	return transport.WithHTTPClient(httpClient)
+}
+
 // NewSSEMCPClient creates a new SSE-based MCP client with the given base URL.
 // Returns an error if the URL is invalid.
 func NewSSEMCPClient(baseURL string, options ...transport.ClientOption) (*Client, error) {

client/transport/sse.go

@@ -45,6 +45,12 @@ func WithHeaders(headers map[string]string) ClientOption {
 	}
 }
 
+func WithHTTPClient(httpClient *http.Client) ClientOption {
+	return func(sc *SSE) {
+		sc.httpClient = httpClient
+	}
+}
+
 // NewSSE creates a new SSE-based MCP client with the given base URL.
 // Returns an error if the URL is invalid.
 func NewSSE(baseURL string, options ...ClientOption) (*SSE, error) {

client/transport/sse_test.go

@@ -415,6 +415,31 @@ func TestSSEErrors(t *testing.T) {
 		}
 	})
 
+	t.Run("WithHTTPClient", func(t *testing.T) {
+		// Create a custom client with a very short timeout
+		customClient := &http.Client{Timeout: 1 * time.Nanosecond}
+
+		url, closeF := startMockSSEEchoServer()
+		defer closeF()
+		// Initialize SSE transport with the custom HTTP client
+		trans, err := NewSSE(url, WithHTTPClient(customClient))
+		if err != nil {
+			t.Fatalf("Failed to create SSE with custom client: %v", err)
+		}
+
+		// Starting should immediately error due to timeout
+		ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
+		defer cancel()
+		err = trans.Start(ctx)
+		if err == nil {
+			t.Error("Expected Start to fail with custom timeout, got nil")
+		}
+		if !errors.Is(err, context.DeadlineExceeded) {
+			t.Errorf("Expected error 'context deadline exceeded', got '%s'", err.Error())
+		}
+		trans.Close()
+	})
+
 	t.Run("RequestBeforeStart", func(t *testing.T) {
 		url, closeF := startMockSSEEchoServer()
 		defer closeF()