add a unit test

main.go

@@ -204,7 +204,11 @@ func toRealPath(p string) string {
 }
 
 func setContentTypeIfMedia(w http.ResponseWriter, r *http.Request) {
-	switch strings.ToLower(path.Ext(r.URL.Path)) {
+	ext := strings.ToLower(path.Ext(r.URL.Path))
+	if i := strings.LastIndex(ext, "."); i != -1 {
+		ext = ext[i:]
+	}
+	switch ext {
 	case ".mp4":
 		w.Header().Set("Content-Type", "video/mp4")
 	case ".mkv":

main_test.go

@@ -0,0 +1,34 @@
+package main
+
+import (
+	"net/http"
+	"net/http/httptest"
+	"net/url"
+	"testing"
+)
+
+func TestSetContentType(t *testing.T) {
+	t.Parallel()
+
+	cases := map[string]struct {
+		path string
+		want string
+	}{
+		"css with multi .": {
+			path: "/static/css/main.2145ce41.chunk.css",
+			want: "text/css",
+		},
+	}
+
+	for name, d := range cases {
+		c := d
+		t.Run(name, func(t *testing.T) {
+			r := &http.Request{URL: &url.URL{Path: c.path}}
+			w := httptest.NewRecorder()
+			setContentTypeIfMedia(w, r)
+			if ct := w.Header().Get("Content-Type"); ct != c.want {
+				t.Errorf("wrong content type: want %q, got %q", c.want, ct)
+			}
+		})
+	}
+}