HTTP。服务器关闭导致运行时错误

我在darwin/amd64上的Go 1.9.2中编写了一个goroutine,它会导致运行时错误:无效的内存地址或零指针解引用。我认为这是因为某种与常规退出顺序相关的比赛条件,但我不确定。

函数如下:

// WebServer defines the handler endpoints and launches the web server listener
func WebServer(wg *sync.WaitGroup) {

    // Make sure the exit is noted
    defer wg.Done()

    // Endpoint, handler function
    http.HandleFunc("/version", WebShowVersion)

    // Go forth and serve
    // Define the server struct
    srv := &http.Server{Addr: ":8080"}

    // Now go serve
    chnToLogger <- "Launching web server on port 8080"
    go func() {
        err := srv.ListenAndServe()
        if err != nil &&
            err.Error() != "http: Server closed" {

            // There...was an error
            chnToLoggerError <- "Error launching web server: " + err.Error()
        }
    }()

    // Listen for a shutdown
    for {
        select {
        case <-chnQuitNow:

            // Shut down the process
            chnToLogger <- "Shutting down web server process"
            if err := srv.Shutdown(nil); err != nil {

                // There was a problem shutting down gracefully
                chnToLoggerError <- "Error shutting down web server: " + err.Error()
                return
            }

            // Done
            chnToLogger <- "Web server has shut down now"
            return

        default:
            continue
        }
    }

    // Done
    return
}

恐慌状态:

panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x28 pc=0x11f7e61]

goroutine 10 [running]:
net/http.(*Server).Shutdown(0xc420158000, 0x0, 0x0, 0x0, 0x0)
    /usr/local/go/src/net/http/server.go:2506 +0x1b1
main.WebServer(0xc4200164a0)
    /Users/me/go/src/testproj/webhandling.go:45 +0x146
created by main.main
    /Users/me/go/src/testproj/main.go:94 +0x3d6

webhandling中的第45行。go是:

if err := srv.Shutdown(nil); err != nil {

虽然它在被触发时并不一致,但似乎只有在我启动程序并使用web客户端多次拉取localhost:8080/version时才会发生这种情况,这让我怀疑srv是否正确。Shutdown(nil)正在尝试关闭具有引用但已退出的连接?

1) 在从goroutine返回之前,是否可以让服务器安全完整地关闭web服务器进程?

2) 是什么导致触发不一致的运行时错误?