go func() {
		if err := s.ListenAndServe(); err != nil && err != http.ErrServerClosed {
			log.Fatalf("s.ListenAndServe err: %v", err)
		}
	}()

func (srv *Server) newConn(rwc net.Conn) *conn {
	c := &conn{
		server: srv,
		rwc:    rwc,
	}
	if debugServerConnections {
		c.rwc = newLoggingConn("server", c.rwc)
	}
	return c
}

func (srv *Server) Serve(l net.Listener) error {
	if fn := testHookServerServe; fn != nil {
		fn(srv, l) // call hook with unwrapped listener
	}

	origListener := l
	l = &onceCloseListener{Listener: l}
	defer l.Close()

	if err := srv.setupHTTP2_Serve(); err != nil {
		return err
	}

	if !srv.trackListener(&l, true) {
		return ErrServerClosed
	}
	defer srv.trackListener(&l, false)

	baseCtx := context.Background()
	if srv.BaseContext != nil {
		baseCtx = srv.BaseContext(origListener)
		if baseCtx == nil {
			panic("BaseContext returned a nil context")
		}
	}

	var tempDelay time.Duration // how long to sleep on accept failure

	ctx := context.WithValue(baseCtx, ServerContextKey, srv)
	for {
		rw, err := l.Accept()
		if err != nil {
			if srv.shuttingDown() {
				return ErrServerClosed
			}
			if ne, ok := err.(net.Error); ok && ne.Temporary() {
				if tempDelay == 0 {
					tempDelay = 5 * time.Millisecond
				} else {
					tempDelay *= 2
				}
				if max := 1 * time.Second; tempDelay > max {
					tempDelay = max
				}
				srv.logf("http: Accept error: %v; retrying in %v", err, tempDelay)
				time.Sleep(tempDelay)
				continue
			}
			return err
		}
		connCtx := ctx
		if cc := srv.ConnContext; cc != nil {
			connCtx = cc(connCtx, rw)
			if connCtx == nil {
				panic("ConnContext returned nil")
			}
		}
		tempDelay = 0
		c := srv.newConn(rw)
		c.setState(c.rwc, StateNew, runHooks) // before Serve can return
		go c.serve(connCtx)
	}
}

// Serve a new connection.
func (c *conn) serve(ctx context.Context) {
	c.remoteAddr = c.rwc.RemoteAddr().String()
	ctx = context.WithValue(ctx, LocalAddrContextKey, c.rwc.LocalAddr())
	var inFlightResponse *response

	// 忽略一些代码

	// 处理TLS
	// ...

	// HTTP/1.x from here on.

	ctx, cancelCtx := context.WithCancel(ctx)
	c.cancelCtx = cancelCtx
	defer cancelCtx()

	c.r = &connReader{conn: c}
	c.bufr = newBufioReader(c.r)
	c.bufw = newBufioWriterSize(checkConnErrorWriter{c}, 4<<10)

	// http 情趣解析重头戏

	for {
		w, err := c.readRequest(ctx)
		if c.r.remain != c.server.initialReadLimitSize() {
			// If we read any bytes off the wire, we're active.
			c.setState(c.rwc, StateActive, runHooks)
		}
		if err != nil {
			const errorHeaders = "\r\nContent-Type: text/plain; charset=utf-8\r\nConnection: close\r\n\r\n"

			switch {
			case err == errTooLarge:
				// Their HTTP client may or may not be
				// able to read this if we're
				// responding to them and hanging up
				// while they're still writing their
				// request. Undefined behavior.
				const publicErr = "431 Request Header Fields Too Large"
				fmt.Fprintf(c.rwc, "HTTP/1.1 "+publicErr+errorHeaders+publicErr)
				c.closeWriteAndWait()
				return

			case isUnsupportedTEError(err):
				// Respond as per RFC 7230 Section 3.3.1 which says,
				//      A server that receives a request message with a
				//      transfer coding it does not understand SHOULD
				//      respond with 501 (Unimplemented).
				code := StatusNotImplemented

				// We purposefully aren't echoing back the transfer-encoding's value,
				// so as to mitigate the risk of cross side scripting by an attacker.
				fmt.Fprintf(c.rwc, "HTTP/1.1 %d %s%sUnsupported transfer encoding", code, StatusText(code), errorHeaders)
				return

			case isCommonNetReadError(err):
				return // don't reply

			default:
				if v, ok := err.(statusError); ok {
					fmt.Fprintf(c.rwc, "HTTP/1.1 %d %s: %s%s%d %s: %s", v.code, StatusText(v.code), v.text, errorHeaders, v.code, StatusText(v.code), v.text)
					return
				}
				publicErr := "400 Bad Request"
				fmt.Fprintf(c.rwc, "HTTP/1.1 "+publicErr+errorHeaders+publicErr)
				return
			}
		}

		// Expect 100 Continue support
		req := w.req
		if req.expectsContinue() {
			if req.ProtoAtLeast(1, 1) && req.ContentLength != 0 {
				// Wrap the Body reader with one that replies on the connection
				req.Body = &expectContinueReader{readCloser: req.Body, resp: w}
				w.canWriteContinue.Store(true)
			}
		} else if req.Header.get("Expect") != "" {
			w.sendExpectationFailed()
			return
		}

		c.curReq.Store(w)

		if requestBodyRemains(req.Body) {
			registerOnHitEOF(req.Body, w.conn.r.startBackgroundRead)
		} else {
			w.conn.r.startBackgroundRead()
		}

		// HTTP cannot have multiple simultaneous active requests.[*]
		// Until the server replies to this request, it can't read another,
		// so we might as well run the handler in this goroutine.
		// [*] Not strictly true: HTTP pipelining. We could let them all process
		// in parallel even if their responses need to be serialized.
		// But we're not going to implement HTTP pipelining because it
		// was never deployed in the wild and the answer is HTTP/2.
		inFlightResponse = w
		serverHandler{c.server}.ServeHTTP(w, w.req)
		inFlightResponse = nil
		w.cancelCtx()
		if c.hijacked() {
			return
		}
		w.finishRequest()
		c.rwc.SetWriteDeadline(time.Time{})
		if !w.shouldReuseConnection() {
			if w.requestBodyLimitHit || w.closedRequestBodyEarly() {
				c.closeWriteAndWait()
			}
			return
		}
		c.setState(c.rwc, StateIdle, runHooks)
		c.curReq.Store(nil)

		if !w.conn.server.doKeepAlives() {
			// We're in shutdown mode. We might've replied
			// to the user without "Connection: close" and
			// they might think they can send another
			// request, but such is life with HTTP/1.1.
			return
		}

		if d := c.server.idleTimeout(); d != 0 {
			c.rwc.SetReadDeadline(time.Now().Add(d))
		} else {
			c.rwc.SetReadDeadline(time.Time{})
		}

		// Wait for the connection to become readable again before trying to
		// read the next request. This prevents a ReadHeaderTimeout or
		// ReadTimeout from starting until the first bytes of the next request
		// have been received.
		if _, err := c.bufr.Peek(4); err != nil {
			return
		}

		c.rwc.SetReadDeadline(time.Time{})
	}
}

// 解析 http 请求
func readRequest(b *bufio.Reader) (req *Request, err error) {
	tp := newTextprotoReader(b)
	defer putTextprotoReader(tp)

	req = new(Request)

	// First line: GET /index.html HTTP/1.0
	var s string
	if s, err = tp.ReadLine(); err != nil {
		return nil, err
	}
	defer func() {
		if err == io.EOF {
			err = io.ErrUnexpectedEOF
		}
	}()

	// 读取请求第一行
	req.Method, req.RequestURI, req.Proto, ok = parseRequestLine(s)

	// 读取请求头
	// Subsequent lines: Key: value.
	mimeHeader, err := tp.ReadMIMEHeader()
	if err != nil {
		return nil, err
	}
	req.Header = Header(mimeHeader)
	if len(req.Header["Host"]) > 1 {
		return nil, fmt.Errorf("too many Host headers")
	}

	// RFC 7230, section 5.3: Must treat
	//	GET /index.html HTTP/1.1
	//	Host: www.google.com
	// and
	//	GET http://www.google.com/index.html HTTP/1.1
	//	Host: doesntmatter
	// the same. In the second case, any Host line is ignored.
	req.Host = req.URL.Host
	if req.Host == "" {
		req.Host = req.Header.get("Host")
	}

	fixPragmaCacheControl(req.Header)

	req.Close = shouldClose(req.ProtoMajor, req.ProtoMinor, req.Header, false)

// 检查是否需要分块读取
	err = readTransfer(req, b)
	if err != nil {
		return nil, err
	}

	if req.isH2Upgrade() {
		// Because it's neither chunked, nor declared:
		req.ContentLength = -1

		// We want to give handlers a chance to hijack the
		// connection, but we need to prevent the Server from
		// dealing with the connection further if it's not
		// hijacked. Set Close to ensure that:
		req.Close = true
	}
	return req, nil
}

// Read next request from connection.
func (c *conn) readRequest(ctx context.Context) (w *response, err error) {
	
	// 一些错误处理逻辑 
	// ...

	

	// 读取报文，按 http 协议解析 ——--> 跳转到上面的那个函数
	req, err := readRequest(c.bufr)
	if err != nil {
		if c.r.hitReadLimit() {
			return nil, errTooLarge
		}
		return nil, err
	}

	if !http1ServerSupportsRequest(req) {
		return nil, statusError{StatusHTTPVersionNotSupported, "unsupported protocol version"}
	}

	c.lastMethod = req.Method
	c.r.setInfiniteReadLimit()

	hosts, haveHost := req.Header["Host"]
	isH2Upgrade := req.isH2Upgrade()
	if req.ProtoAtLeast(1, 1) && (!haveHost || len(hosts) == 0) && !isH2Upgrade && req.Method != "CONNECT" {
		return nil, badRequestError("missing required Host header")
	}
	if len(hosts) == 1 && !httpguts.ValidHostHeader(hosts[0]) {
		return nil, badRequestError("malformed Host header")
	}
	for k, vv := range req.Header {
		if !httpguts.ValidHeaderFieldName(k) {
			return nil, badRequestError("invalid header name")
		}
		for _, v := range vv {
			if !httpguts.ValidHeaderFieldValue(v) {
				return nil, badRequestError("invalid header value")
			}
		}
	}
	delete(req.Header, "Host")

	ctx, cancelCtx := context.WithCancel(ctx)
	req.ctx = ctx
	req.RemoteAddr = c.remoteAddr
	req.TLS = c.tlsState

// 将 req.Body 接口实例化为一个对象，由用户来手动读取 htto请求体
	if body, ok := req.Body.(*body); ok {
		body.doEarlyClose = true
	}

	// Adjust the read deadline if necessary.
	if !hdrDeadline.Equal(wholeReqDeadline) {
		c.rwc.SetReadDeadline(wholeReqDeadline)
	}

	w = &response{
		conn:          c,
		cancelCtx:     cancelCtx,
		req:           req,
		reqBody:       req.Body,
		handlerHeader: make(Header),
		contentLength: -1,
		closeNotifyCh: make(chan bool, 1),

		// We populate these ahead of time so we're not
		// reading from req.Header after their Handler starts
		// and maybe mutates it (Issue 14940)
		wants10KeepAlive: req.wantsHttp10KeepAlive(),
		wantsClose:       req.wantsClose(),
	}
	if isH2Upgrade {
		w.closeAfterReply = true
	}
	w.cw.res = w
	w.w = newBufioWriterSize(&w.cw, bufferBeforeChunkingSize)
	return w, nil
}

// msg is *Request or *Response.
func readTransfer(msg any, r *bufio.Reader) (err error) {
	t := &transferReader{RequestMethod: "GET"}

	// Unify input
	isResponse := false
	switch rr := msg.(type) {
	case *Response:
		t.Header = rr.Header
		t.StatusCode = rr.StatusCode
		t.ProtoMajor = rr.ProtoMajor
		t.ProtoMinor = rr.ProtoMinor
		t.Close = shouldClose(t.ProtoMajor, t.ProtoMinor, t.Header, true)
		isResponse = true
		if rr.Request != nil {
			t.RequestMethod = rr.Request.Method
		}
	case *Request:
		t.Header = rr.Header
		t.RequestMethod = rr.Method
		t.ProtoMajor = rr.ProtoMajor
		t.ProtoMinor = rr.ProtoMinor
		// Transfer semantics for Requests are exactly like those for
		// Responses with status code 200, responding to a GET method
		t.StatusCode = 200
		t.Close = rr.Close
	default:
		panic("unexpected type")
	}

	// Default to HTTP/1.1
	if t.ProtoMajor == 0 && t.ProtoMinor == 0 {
		t.ProtoMajor, t.ProtoMinor = 1, 1
	}

	// Transfer-Encoding: chunked, and overriding Content-Length.
	if err := t.parseTransferEncoding(); err != nil {
		return err
	}

	realLength, err := fixLength(isResponse, t.StatusCode, t.RequestMethod, t.Header, t.Chunked)
	if err != nil {
		return err
	}
	if isResponse && t.RequestMethod == "HEAD" {
		if n, err := parseContentLength(t.Header.get("Content-Length")); err != nil {
			return err
		} else {
			t.ContentLength = n
		}
	} else {
		t.ContentLength = realLength
	}

	// Trailer
	t.Trailer, err = fixTrailer(t.Header, t.Chunked)
	if err != nil {
		return err
	}

	// If there is no Content-Length or chunked Transfer-Encoding on a *Response
	// and the status is not 1xx, 204 or 304, then the body is unbounded.
	// See RFC 7230, section 3.3.
	switch msg.(type) {
	case *Response:
		if realLength == -1 && !t.Chunked && bodyAllowedForStatus(t.StatusCode) {
			// Unbounded body.
			t.Close = true
		}
	}

	// Prepare body reader. ContentLength < 0 means chunked encoding
	// or close connection when finished, since multipart is not supported yet
	switch {
	case t.Chunked:
		if isResponse && (noResponseBodyExpected(t.RequestMethod) || !bodyAllowedForStatus(t.StatusCode)) {
			t.Body = NoBody
		} else {
			t.Body = &body{src: internal.NewChunkedReader(r), hdr: msg, r: r, closing: t.Close}
		}
	case realLength == 0:
		t.Body = NoBody
	case realLength > 0:
		t.Body = &body{src: io.LimitReader(r, realLength), closing: t.Close}
	default:
		// realLength < 0, i.e. "Content-Length" not mentioned in header
		if t.Close {
			// Close semantics (i.e. HTTP/1.0)
			t.Body = &body{src: r, closing: t.Close}
		} else {
			// Persistent connection (i.e. HTTP/1.1)
			t.Body = NoBody
		}
	}

	// Unify output
	switch rr := msg.(type) {
	case *Request:
		rr.Body = t.Body
		rr.ContentLength = t.ContentLength
		if t.Chunked {
			rr.TransferEncoding = []string{"chunked"}
		}
		rr.Close = t.Close
		rr.Trailer = t.Trailer
	case *Response:
		rr.Body = t.Body
		rr.ContentLength = t.ContentLength
		if t.Chunked {
			rr.TransferEncoding = []string{"chunked"}
		}
		rr.Close = t.Close
		rr.Trailer = t.Trailer
	}

	return nil
}

// Serve a new connection.
func (c *conn) serve(ctx context.Context) {
	c.remoteAddr = c.rwc.RemoteAddr().String()
	ctx = context.WithValue(ctx, LocalAddrContextKey, c.rwc.LocalAddr())
	var inFlightResponse *response

	// 忽略一些代码

	// 处理TLS
	// ...

	// HTTP/1.x from here on.

	ctx, cancelCtx := context.WithCancel(ctx)
	c.cancelCtx = cancelCtx
	defer cancelCtx()

	c.r = &connReader{conn: c}
	c.bufr = newBufioReader(c.r)
	c.bufw = newBufioWriterSize(checkConnErrorWriter{c}, 4<<10)

	// http 情趣解析重头戏

	for {
		w, err := c.readRequest(ctx)
		

		// 删去了一些错误处理，让代码主逻辑体现出来

		// HTTP cannot have multiple simultaneous active requests.[*]
		// Until the server replies to this request, it can't read another,
		// so we might as well run the handler in this goroutine.
		// [*] Not strictly true: HTTP pipelining. We could let them all process
		// in parallel even if their responses need to be serialized.
		// But we're not going to implement HTTP pipelining because it
		// was never deployed in the wild and the answer is HTTP/2.
		inFlightResponse = w

		

		// 这里调用的 ServerHTTP 函数其实就是 我们在 main 函数中传入的 handler （其实也就是路由殷勤）
		router := routers.NewRouter()
		//		s := &http.Server{
		//			Addr:           ":" + global.ServerSetting.HttpPort,
		//			Handler:        router,
		//			ReadTimeout:    global.ServerSetting.ReadTimeout,
		//			WriteTimeout:   global.ServerSetting.WriteTimeout,
		//			MaxHeaderBytes: 1 << 20,
		//		}
		serverHandler{c.server}.ServeHTTP(w, w.req)

	
		// 做一些收尾工作，例如心跳机制等
		// .....

	}
}

type serverHandler struct {
	srv *Server
}

type conn struct {
	// server is the server on which the connection arrived.
	// Immutable; never nil.
	server *Server

	// cancelCtx cancels the connection-level context.
	cancelCtx context.CancelFunc

	// rwc is the underlying network connection.
	// This is never wrapped by other types and is the value given out
	// to CloseNotifier callers. It is usually of type *net.TCPConn or
	// *tls.Conn.
	rwc net.Conn

	// remoteAddr is rwc.RemoteAddr().String(). It is not populated synchronously
	// inside the Listener's Accept goroutine, as some implementations block.
	// It is populated immediately inside the (*conn).serve goroutine.
	// This is the value of a Handler's (*Request).RemoteAddr.
	remoteAddr string

	// tlsState is the TLS connection state when using TLS.
	// nil means not TLS.
	tlsState *tls.ConnectionState

	// werr is set to the first write error to rwc.
	// It is set via checkConnErrorWriter{w}, where bufw writes.
	werr error

	// r is bufr's read source. It's a wrapper around rwc that provides
	// io.LimitedReader-style limiting (while reading request headers)
	// and functionality to support CloseNotifier. See *connReader docs.
	r *connReader

	// bufr reads from r.
	bufr *bufio.Reader

	// bufw writes to checkConnErrorWriter{c}, which populates werr on error.
	bufw *bufio.Writer

	// lastMethod is the method of the most recent request
	// on this connection, if any.
	lastMethod string

	curReq atomic.Pointer[response] // (which has a Request in it)

	curState atomic.Uint64 // packed (unixtime<<8|uint8(ConnState))

	// mu guards hijackedv
	mu sync.Mutex

	// hijackedv is whether this connection has been hijacked
	// by a Handler with the Hijacker interface.
	// It is guarded by mu.
	hijackedv bool
}

	//  main()
	//			router := routers.NewRouter()
	//			s := &http.Server{
	//				Addr:           ":" + global.ServerSetting.HttpPort,
	//				Handler:        router,
	//				ReadTimeout:    global.ServerSetting.ReadTimeout,
	//				WriteTimeout:   global.ServerSetting.WriteTimeout,
	//				MaxHeaderBytes: 1 << 20,
	//			}

func (sh serverHandler) ServeHTTP(rw ResponseWriter, req *Request) {

	// 获取 main 函数中创建的 server ，将这个server 的 handler 对象，也就是 router 路由引擎单独拿出来
	handler := sh.srv.Handler
	if handler == nil {
		handler = DefaultServeMux
	}
	if !sh.srv.DisableGeneralOptionsHandler && req.RequestURI == "*" && req.Method == "OPTIONS" {
		handler = globalOptionsHandler{}
	}

	if req.URL != nil && strings.Contains(req.URL.RawQuery, ";") {
		var allowQuerySemicolonsInUse atomic.Bool
		req = req.WithContext(context.WithValue(req.Context(), silenceSemWarnContextKey, func() {
			allowQuerySemicolonsInUse.Store(true)
		}))
		defer func() {
			if !allowQuerySemicolonsInUse.Load() {
				sh.srv.logf("http: URL query contains semicolon, which is no longer a supported separator; parts of the query may be stripped when parsed; see golang.org/issue/25192")
			}
		}()
	}

	handler.ServeHTTP(rw, req)
}

type Engine struct {
	RouterGroup

	// Enables automatic redirection if the current route can't be matched but a
	// handler for the path with (without) the trailing slash exists.
	// For example if /foo/ is requested but a route only exists for /foo, the
	// client is redirected to /foo with http status code 301 for GET requests
	// and 307 for all other request methods.
	RedirectTrailingSlash bool

	// If enabled, the router tries to fix the current request path, if no
	// handle is registered for it.
	// First superfluous path elements like ../ or // are removed.
	// Afterwards the router does a case-insensitive lookup of the cleaned path.
	// If a handle can be found for this route, the router makes a redirection
	// to the corrected path with status code 301 for GET requests and 307 for
	// all other request methods.
	// For example /FOO and /..//Foo could be redirected to /foo.
	// RedirectTrailingSlash is independent of this option.
	RedirectFixedPath bool

	// If enabled, the router checks if another method is allowed for the
	// current route, if the current request can not be routed.
	// If this is the case, the request is answered with 'Method Not Allowed'
	// and HTTP status code 405.
	// If no other Method is allowed, the request is delegated to the NotFound
	// handler.
	HandleMethodNotAllowed bool
	ForwardedByClientIP    bool

	// #726 #755 If enabled, it will thrust some headers starting with
	// 'X-AppEngine...' for better integration with that PaaS.
	AppEngine bool

	// If enabled, the url.RawPath will be used to find parameters.
	UseRawPath bool

	// If true, the path value will be unescaped.
	// If UseRawPath is false (by default), the UnescapePathValues effectively is true,
	// as url.Path gonna be used, which is already unescaped.
	UnescapePathValues bool

	// Value of 'maxMemory' param that is given to http.Request's ParseMultipartForm
	// method call.
	MaxMultipartMemory int64

	// RemoveExtraSlash a parameter can be parsed from the URL even with extra slashes.
	// See the PR #1817 and issue #1644
	RemoveExtraSlash bool

	delims           render.Delims
	secureJsonPrefix string
	HTMLRender       render.HTMLRender
	FuncMap          template.FuncMap
	allNoRoute       HandlersChain
	allNoMethod      HandlersChain
	noRoute          HandlersChain
	noMethod         HandlersChain
	pool             sync.Pool
	trees            methodTrees   // 前缀树
}

// ServeHTTP conforms to the http.Handler interface.
func (engine *Engine) ServeHTTP(w http.ResponseWriter, req *http.Request) {
	c := engine.pool.Get().(*Context)
	c.writermem.reset(w)
	c.Request = req
	c.reset()

	engine.handleHTTPRequest(c)

	engine.pool.Put(c)
}

func (engine *Engine) handleHTTPRequest(c *Context) {
	httpMethod := c.Request.Method
	rPath := c.Request.URL.Path
	unescape := false
	if engine.UseRawPath && len(c.Request.URL.RawPath) > 0 {
		rPath = c.Request.URL.RawPath
		unescape = engine.UnescapePathValues
	}

	if engine.RemoveExtraSlash {
		rPath = cleanPath(rPath)
	}

	// Find root of the tree for the given HTTP method
	t := engine.trees
	for i, tl := 0, len(t); i < tl; i++ {
		if t[i].method != httpMethod {
			continue
		}
		root := t[i].root
		// Find route in tree
		value := root.getValue(rPath, c.Params, unescape)
		if value.handlers != nil {
			c.handlers = value.handlers
			c.Params = value.params
			c.fullPath = value.fullPath
			c.Next()  // 执行节点上用户注册的的路由的处理函数 handler 
			c.writermem.WriteHeaderNow()
			return
		}
		if httpMethod != "CONNECT" && rPath != "/" {
			if value.tsr && engine.RedirectTrailingSlash {
				redirectTrailingSlash(c)
				return
			}
			if engine.RedirectFixedPath && redirectFixedPath(c, root, engine.RedirectFixedPath) {
				return
			}
		}
		break
	}

	if engine.HandleMethodNotAllowed {
		for _, tree := range engine.trees {
			if tree.method == httpMethod {
				continue
			}
			if value := tree.root.getValue(rPath, nil, unescape); value.handlers != nil {
				c.handlers = engine.allNoMethod
				serveError(c, http.StatusMethodNotAllowed, default405Body)
				return
			}
		}
	}
	c.handlers = engine.allNoRoute
	serveError(c, http.StatusNotFound, default404Body)
}

// 迭代器，依次执行 handler
func (c *Context) Next() {
	c.index++
	for c.index < int8(len(c.handlers)) {
		c.handlers[c.index](c)
		c.index++
	}
}

// 树的根节点
type methodTree struct {
	method string
	root   *node
}


// 树的节点
type nodeValue struct {
	handlers HandlersChain
	params   Params
	tsr      bool
	fullPath string
}