http.go

func main() {
    // how we start a http server
    http.HandleFunc("/user", handler)
    http.ListenAndServe(":8080", nil)
}

// src/net/http/server.go
func ListenAndServe(addr string, handler Handler) error {
    server := &Server{Addr: addr, Handler: handler}
    return server.ListenAndServe()
}

func (srv *Server) ListenAndServe() error {
    addr := srv.Addr
    if addr == "" {
        addr = ":http"
    }
    ln, err := net.Listen("tcp", addr)
    if err != nil {
        return err
    }
    return srv.Serve(tcpKeepAliveListener{ln.(*net.TCPListener)})
}

func (srv *Server) Serve(l net.Listener) error {
    // ...
    for {
        rw, e := l.Accept()
        if e != nil {
            // 处理错误
            return e
        }
        tempDelay = 0
        c := srv.newConn(rw)
        c.setState(c.rwc, StateNew) // before Serve can return
        go c.serve(ctx)
    }
}

func (c *conn) serve(ctx context.Context) {
    // pre handle
    for {
        w, err := c.readRequest(ctx)
        // handle w and err

        serverHandler{c.server}.ServeHTTP(w, w.req)
        // post handle
    }
}

type serverHandler struct {
    srv *Server
}

func (sh serverHandler) ServeHTTP(rw ResponseWriter, req *Request) {
    handler := sh.srv.Handler
    if handler == nil {
        handler = DefaultServeMux
    }
    if req.RequestURI == "*" && req.Method == "OPTIONS" {
        handler = globalOptionsHandler{}
    }
    handler.ServeHTTP(rw, req)
}