ListenAndServe

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

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 {
         select {
         case <-srv.getDoneChan():
            return ErrServerClosed
         default:
         }
         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)
   }
}

每个请求都会开启一个go routine 执行 c.serve