這些天，Goroutines 和通道困擾著我。我正在查看https://github.com/adonovan/gopl.io/tree/master/ch9上的 memo5 代碼。如果你看 memo5 的 memo.go，有func (e *entry) call(f Func, key string)和func (e *entry) deliver(response chan<- result)部分。// Copyright ? 2016 Alan A. A. Donovan & Brian W. Kernighan.// License: https://creativecommons.org/licenses/by-nc-sa/4.0/// See page 278.// Package memo provides a concurrency-safe non-blocking memoization// of a function.  Requests for different keys proceed in parallel.// Concurrent requests for the same key block until the first completes.// This implementation uses a monitor goroutine.package memo//!+Func// Func is the type of the function to memoize.type Func func(key string) (interface{}, error)// A result is the result of calling a Func.type result struct {    value interface{}    err   error}type entry struct {    res   result    ready chan struct{} // closed when res is ready}//!-Func//!+get// A request is a message requesting that the Func be applied to key.type request struct {    key      string    response chan<- result // the client wants a single result}type Memo struct{ requests chan request }// New returns a memoization of f.  Clients must subsequently call Close.func New(f Func) *Memo {    memo := &Memo{requests: make(chan request)}    go memo.server(f)    return memo}func (memo *Memo) Get(key string) (interface{}, error) {    response := make(chan result)    memo.requests <- request{key, response}    res := <-response    return res.value, res.err}我不明白如何在 close(e.ready)這里 <-e.ready同步。就算看完書，也看不懂。請告訴我機制是什么。