fix(writer): panic occurred while processing redirect request (#37)

* fix: do not panic on status code -1

* test: update test to include verifying that no header was written

---------

Co-authored-by: Bo-Yi Wu <appleboy.tw@gmail.com>

writer.go

@@ -41,11 +41,18 @@ func (w *Writer) Write(data []byte) (int, error) {
 // If the response writer has already written headers or if a timeout has occurred,
 // this method does nothing.
 func (w *Writer) WriteHeader(code int) {
-	checkWriteHeaderCode(code)
 	if w.timeout || w.wroteHeaders {
 		return
 	}
 
+	// gin is using -1 to skip writing the status code
+	// see https://github.com/gin-gonic/gin/blob/a0acf1df2814fcd828cb2d7128f2f4e2136d3fac/response_writer.go#L61
+	if code == -1 {
+		return
+	}
+
+	checkWriteHeaderCode(code)
+
 	w.mu.Lock()
 	defer w.mu.Unlock()
 

writer_test.go

@@ -28,6 +28,16 @@ func TestWriteHeader(t *testing.T) {
 	})
 }
 
+func TestWriteHeader_SkipMinusOne(t *testing.T) {
+	code := -1
+
+	writer := Writer{}
+	assert.NotPanics(t, func() {
+		writer.WriteHeader(code)
+		assert.False(t, writer.wroteHeaders)
+	})
+}
+
 func TestWriter_Status(t *testing.T) {
 	r := gin.New()