fix: serve index.html via FileFromFS without redirect

Serve regular files from FileFromFS directly with http.ServeContent so file names ending in index.html are returned as requested instead of triggering net/http FileServer's directory redirect behavior. Directory paths continue to use FileServer.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

context.go

@@ -1339,6 +1339,24 @@ func (c *Context) File(filepath string) {
 
 // FileFromFS writes the specified file from http.FileSystem into the body stream in an efficient way.
 func (c *Context) FileFromFS(filepath string, fs http.FileSystem) {
+	file, err := fs.Open(filepath)
+	if err != nil {
+		http.NotFound(c.Writer, c.Request)
+		return
+	}
+	defer file.Close()
+
+	info, err := file.Stat()
+	if err != nil {
+		http.NotFound(c.Writer, c.Request)
+		return
+	}
+
+	if !info.IsDir() {
+		http.ServeContent(c.Writer, c.Request, filepath, info.ModTime(), file)
+		return
+	}
+
 	defer func(old string) {
 		c.Request.URL.Path = old
 	}(c.Request.URL.Path)

context_test.go

@@ -25,6 +25,7 @@ import (
 	"strings"
 	"sync"
 	"testing"
+	"testing/fstest"
 	"time"
 
 	"github.com/gin-contrib/sse"
@@ -1558,6 +1559,21 @@ func TestContextRenderFileFromFS(t *testing.T) {
 	assert.Equal(t, "/some/path", c.Request.URL.Path)
 }
 
+func TestContextRenderFileFromFSIndexHTML(t *testing.T) {
+	w := httptest.NewRecorder()
+	c, _ := CreateTestContext(w)
+
+	c.Request, _ = http.NewRequest(http.MethodGet, "/", nil)
+	c.FileFromFS("www/index.html", http.FS(fstest.MapFS{
+		"www/index.html": {Data: []byte("index")},
+	}))
+
+	assert.Equal(t, http.StatusOK, w.Code)
+	assert.Equal(t, "index", w.Body.String())
+	assert.Empty(t, w.Header().Get("Location"))
+	assert.Equal(t, "/", c.Request.URL.Path)
+}
+
 func TestContextRenderAttachment(t *testing.T) {
 	w := httptest.NewRecorder()
 	c, _ := CreateTestContext(w)