用go搭一个简单的web 服务器，如何设置error 和port flag

```go package main import ( "flag" "fmt" ) func main() { version := flag.Bool("version", false, "Print the version and exit") //Needto add `debug` and `port` flags below, and how? flag.Parse() if *version { fmt.Printf("FCON 1.0") return } //needto Initialize Server, assign to `s` Below, and how? s.run() } ```