可否增加https 证书自定义？

`var err error
if gcfg.Key != "" && gcfg.Cert != "" {
err = srv.ListenAndServeTLS(gcfg.Cert, gcfg.Key)
} else {
err = srv.ListenAndServe()
}
`
看大佬写了但是 实际没有去用上面的证书相关代码，可否使用环境变量去控制赋值或者指定路径读取如果失败再走http，这样docker 可以直接映射进去，就方便很多了。

Start at the server setup containing gcfg.Key, gcfg.Cert, srv.ListenAndServeTLS, and srv.ListenAndServe. Trace how configuration is populated, then add the requested environment-variable or path-based certificate handling and verify that HTTP remains the fallback when certificate loading fails.

Written by the indexing model from the issue text.