解釋伺服器的幾個概念：
1. Request 使用者請求的資訊
2. Response 伺服器返回的資訊
3. Conn 使用者的每次請求連結
4. Handler 處理請求和生成返回資訊的處理邏輯

先寫個小程式看看

func MyConn() {
    // 監聽9090埠
    listener, _ := net.Listen("tcp", "localhost:9090")
    defer listener.Close()

    // 建立使用者請求的連線
    conn, _ := listener.Accept()
    defer conn.Close()

    // 讀取Request的內容
 

    buff := make([]byte, 10000)
    len, _ := conn.Read(buff)
    fmt.Fprintln(os.Stdout, string(buff[:len]))
}

對於程式碼，要解釋的是讀取conn的內容，你可以把conn看做是資料流，先看下Golang中的原始碼，先不去掉註釋，Golang的註釋真的是簡單好懂，看完了註釋，你就應該能理解Conn是什麼了。

// Multiple goroutines may invoke methods on a Conn simultaneously.
type Conn interface {
    // Read
 
 reads data from the connection.
    // Read can be made to time out and return an Error with Timeout() == true
    // after a fixed time limit; see SetDeadline and SetReadDeadline.
    Read(b []byte) (n int, err error)

    // Write writes data to the connection.
    // Write can be made to time out and return
 
 an Error with Timeout() == true
    // after a fixed time limit; see SetDeadline and SetWriteDeadline.
    Write(b []byte) (n int, err error)

    // Close closes the connection.
    // Any blocked Read or Write operations will be unblocked and return errors.
    Close() error

    // LocalAddr returns the local network address.
    LocalAddr() Addr

    // RemoteAddr returns the remote network address.
    RemoteAddr() Addr

    // SetDeadline sets the read and write deadlines associated
    // with the connection. It is equivalent to calling both
    // SetReadDeadline and SetWriteDeadline.
    //
    // A deadline is an absolute time after which I/O operations
    // fail with a timeout (see type Error) instead of
    // blocking. The deadline applies to all future and pending
    // I/O, not just the immediately following call to Read or
    // Write. After a deadline has been exceeded, the connection
    // can be refreshed by setting a deadline in the future.
    //
    // An idle timeout can be implemented by repeatedly extending
    // the deadline after successful Read or Write calls.
    //
    // A zero value for t means I/O operations will not time out.
    SetDeadline(t time.Time) error

    // SetReadDeadline sets the deadline for future Read calls
    // and any currently-blocked Read call.
    // A zero value for t means Read will not time out.
    SetReadDeadline(t time.Time) error

    // SetWriteDeadline sets the deadline for future Write calls
    // and any currently-blocked Write call.
    // Even if write times out, it may return n > 0, indicating that
    // some of the data was successfully written.
    // A zero value for t means Write will not time out.
    SetWriteDeadline(t time.Time) error
}

在瀏覽器上輸入 localhost:9090 ，按下回車鍵，你的命令列會有一下的內容

GET / HTTP/1.1          //請求行：請求方法(GET), 請求的URL(/)，HTTP協議(HTTP/1.1)
Host: localhost:9090        //伺服器主機名
User-Agent: Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:61.0) Gecko/20100101 Firefox/61.0    //瀏覽器資訊
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8 //客戶端能接受的mine
Accept-Language: zh-CN,en-US;q=0.7,en;q=0.3 //請求頭允許客戶端宣告它可以理解的自然語言，以及優先選擇的區域方言
Accept-Encoding: gzip, deflate //是否支援流壓縮
Connection: keep-alive      //控制當前傳輸結束後是否保持網路連線
Upgrade-Insecure-Requests: 1    //Sends a signal to the server expressing the client’s preference for an encrypted and authenticated response, and that it can successfully handle the upgrade-insecure-requests directive.
//空行，分割請求頭和訊息體
//訊息體，POST傳遞

關於請求頭資料的更詳細的資料可以看https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers

目前比較重要的是這個資料的第一行

GET / HTTP/1.1  

如果你在位址列輸入的網址是 localhost:9090/hello ，第一行會是這樣

GET /hello HTTP/1.1 

對於伺服器，首先需要知道協議（是GET還是POST），然後需要知道你想要訪問的地址。對於瞭解MVC的同學肯定了解Controller，在Golang中，也存在類似的路由機制，你可以將訪問的URL跟Handler一一對應（感覺是不是有點像鍵值對），根據請求的URL就可以對請求內容進行操作並返回了，先寫到這裡，下一節再想想怎麼寫Handler.