Golang中TCP服务器/客户端使用io.CopyN()卡住的问题

Golang中TCP服务器/客户端使用io.CopyN()卡住的问题 我正在尝试制作一个用于传输文件的TCP服务器。我使用io.CopyN进行读写操作。从服务器端，我将文件发送给客户端，服务器端可以完美发送所有字节，但客户端在读取大约1000000字节后会卡住。有时工作正常，有时会卡住。我使用300MB的PDF文件进行测试。以下是相关代码和输出：

//server

package main

import (
"fmt"
"io"
"log"
"net"
"os"
"strconv"
"strings"
)

func main() {

fmt.Println("In server \n")

ls, err := net.Listen("tcp", ":1234")

defer ls.Close()

if err != nil {

	panic(err)

}

i := 1

for {

	conn, _ := ls.Accept()
	var check string
	var check1 string

	defer conn.Close()

	for {
		fmt.Println("Do you want to send more : ")
		fmt.Scanf("%s", &check1)

		if check == "n" {

			break

		}

		file, err := os.Open(strings.TrimSpace("./" + "Mag" + ".pdf"))

		if err != nil {

			fmt.Println("inside error 111 : ", i)
			log.Fatal(err)
		}

		defer file.Close()

		fileInfo, err := file.Stat()

		if err != nil {

			fmt.Println("in stat")
		}

		size := fileInfo.Size()

		numberOfTime := size / 1000000

		leftByte := size - numberOfTime*1000000

		numberOfTimeString := strconv.Itoa(int(numberOfTime))
		leftByteString := strconv.Itoa(int(leftByte))

		fmt.Println("1000000 times : ", numberOfTimeString)

		fmt.Println("Left Bytes : ", leftByteString)

		sizeSent, err := fmt.Fprintf(conn, numberOfTimeString+"\n")

		if err != nil {

			panic(err)

		}

		sizeSent, err = fmt.Fprintf(conn, leftByteString+"\n")

		if err != nil {

			panic(err)

		}

		fmt.Println(sizeSent)

		fileWriter := io.Writer(conn)

		n, err := io.CopyN(fileWriter, file, size)

		if err == io.EOF {
			fmt.Println(err, n)
		}

		fmt.Println(n, "bytes sent")

		if err != nil {

			log.Println(err)

		}

		file.Close()

	}

}

fmt.Println("We are done with server")

}

//client

package main

 import (
"bufio"
"fmt"
"io"
"io/ioutil"
"log"
"net"
"os"
"os/signal"
"strconv"
"strings"
"syscall"
 )

func main() {

c := make(chan os.Signal, 15)
signal.Notify(c, syscall.SIGINT)

go func() {

	for {
		s := <-c

		switch s {

		case syscall.SIGINT:
			removeDir()
			os.Exit(1)
		}

	}

}()

defer removeDir()

conn, err := net.Dial("tcp", ":1234")

if err != nil {

	panic(err)

}

defer conn.Close()

connReadWrite := bufio.NewReader(io.Reader(conn))

var i int
var filename string

for {

	i++
	if i > 15 {
		break
	}

	nu := strconv.Itoa(i)
	os.MkdirAll("./"+nu+"/", os.ModePerm)

	filename = "./" + nu + "/image" + nu + ".pdf"

	file, err := os.Create(filename)

	defer file.Close()

	if err != nil {
		panic(err)
	}

	l1, err := connReadWrite.ReadString('\n')

	if err != nil {

		println(err)
	}

	println("\n1000000 times :", l1)

	l1 = strings.TrimSuffix(l1, "\n")

	nb1, err := strconv.Atoi(l1)

	if err != nil {

		panic(err)
	}

	l2, err := connReadWrite.ReadString('\n')

	if err != nil {

		println(err)
	}

	println("Left Bytes :", l2)

	l2 = strings.TrimSuffix(l2, "\n")

	nb2, err := strconv.Atoi(l2)

	if err != nil {

		panic(err)
	}

	fmt.Println("After convert in Num :", nb1, nb2)

	newFileWriter := io.Writer(file)
	newFileReader := io.Reader(conn)

	for i := 0; i < nb1; i++ {

		n, err := io.CopyN(newFileWriter, newFileReader, 1000000)

		if i >= 31 {
			errFun(err, n)
		}
	}

	n, err := io.CopyN(newFileWriter, newFileReader, int64(nb2))
	errFun(err, n)

	file.Close()

}

fmt.Println("We are done with client ")
}

func errFun(err error, n int64) {

if err == io.EOF {

	fmt.Println("End of file : ", n)
	return

} else if n == 0 {

	fmt.Println("n is : ", n)
	return

} else if err != nil {
	fmt.Println(err)
	return

}

fmt.Println(err, " : ", n)
}

func removeDir() {

var dir []string

files, err := ioutil.ReadDir("./")
if err != nil {
	log.Fatal(err)
}

for _, f := range files {
	dir = append(dir, f.Name())
}

for i, dname := range dir {

	if i < 1 {
		continue
	}

	file, err := os.Open("./" + dname)

	fileInfo, err := file.Stat()

	if !fileInfo.IsDir() {

		file.Close()
		continue

	}

	err = os.RemoveAll(dname)

	if err != nil {
		log.Fatal(err)
	}

	file.Close()

}

输入/输出

从服务器端，当按下Y时发送数据，客户端获取需要读取的字节数，然后我发送文件，客户端进行读取。在图片中，我能够发送两次，但第三次会卡住，有时第一次也会卡住。当卡住时如果按下Ctrl+C，会得到文件结束错误。我实在无法理解这个问题。