fix: set header keys only if not set previously

utils.go

@@ -93,8 +93,11 @@ func readHeaders(rb *bufio.Reader) (map[string]string, error) {
 			return nil, err
 		}
 
+		// set only if not set previously
+		if _, ok := ret[key]; !ok {
 			ret[key] = val
 		}
+	}
 
 	return ret, nil
 }