Fix golangci-lint warnings (#17598 et al) (#17668)

Backport #17598 
Backport #17606 
Backport #17608 
Backport #17609

- Since https://gitea.com/gitea/test-env/pulls/10 the golangci-lint has been upgraded and is erroring about new warnings in the code, this PR fixes those warnings.

build.go

@@ -2,7 +2,8 @@
 // Use of this source code is governed by a MIT-style
 // license that can be found in the LICENSE file.
 
-//+build vendor
+//go:build vendor
+// +build vendor
 
 package main