Prevent caching for dynamic directory

Signed-off-by: Vishal Rana <vr@labstack.com>

echo.go

@@ -418,9 +418,10 @@ func (e *Echo) serveFile(dir, file string, c *Context) (err error) {
 
 	fi, _ := f.Stat()
 	if fi.IsDir() {
-		if checkLastModified(c.response, c.request, fi.ModTime()) {
+		/* NOTE:
-			return
+		Not checking the Last-Modified header as it caches the response `304` when
-		}
+		changing differnt directories for the same path.
+		*/
 		d := f
 
 		// Index file
@@ -693,25 +694,3 @@ func (binder) Bind(r *http.Request, i interface{}) (err error) {
 	}
 	return
 }
-
-// Source: net/http/fs.go
-func checkLastModified(w http.ResponseWriter, r *http.Request, modtime time.Time) bool {
-	if modtime.IsZero() || modtime.Equal(unixEpochTime) {
-		// If the file doesn't have a modtime (IsZero), or the modtime
-		// is obviously garbage (Unix time == 0), then ignore modtimes
-		// and don't process the If-Modified-Since header.
-		return false
-	}
-
-	// The Date-Modified header truncates sub-second precision, so
-	// use mtime < t+1s instead of mtime <= t to check for unmodified.
-	if t, err := time.Parse(http.TimeFormat, r.Header.Get("If-Modified-Since")); err == nil && modtime.Before(t.Add(1*time.Second)) {
-		h := w.Header()
-		delete(h, "Content-Type")
-		delete(h, "Content-Length")
-		w.WriteHeader(http.StatusNotModified)
-		return true
-	}
-	w.Header().Set("Last-Modified", modtime.UTC().Format(http.TimeFormat))
-	return false
-}