errors: Pointer to handler prevents nil pointer errors in handling (fixes #15)

If we do not use a pointer here, the startup function that opens the log file stores the log file in a copy of the handler, not the same instance of the handler, causing panics during requests, which is bad, especially when the response is gzipped: the next recover() is beyond the gzip handler, so the browser downloads a gz file instead.

middleware/errors/errors.go

@@ -113,8 +113,11 @@ func (h ErrorHandler) errorPage(w http.ResponseWriter, code int) {
 	http.Error(w, defaultBody, code)
 }
 
-func parse(c middleware.Controller) (ErrorHandler, error) {
-	handler := ErrorHandler{ErrorPages: make(map[int]string)}
+func parse(c middleware.Controller) (*ErrorHandler, error) {
+	// Very important that we make a pointer because the Startup
+	// function that opens the log file must have access to the
+	// same instance of the handler, not a copy.
+	handler := &ErrorHandler{ErrorPages: make(map[int]string)}
 
 	optionalBlock := func() (bool, error) {
 		var hadBlock bool