补充 self signed 期限

Software/Application/Caddy/Caddy_的使用.md

@@ -102,3 +102,11 @@ TLS 必须满足以下要求才能保证 HTTPS 功能正常：
 * TLS is not turned off in site's definition
 * Certificates and keys are not provided by you
 * Caddy is able to bind to ports 80 and 443 (unless you use the DNS challenge)
+
+## 修改 self signed 期限
+
+修改如下代码：  
+
+```go
+selfsigned.go:47:notAfter = notBefore.Add(24 * time.Hour * 7)
+```