Go 언어의 네트워크 프로그래밍 기능을 사용하여 FTP 클라이언트 업로드 파일을 구현하는 방법은 무엇입니까?

package main

import (
    "fmt"
    "io"
    "log"
    "net"
    "os"
    "path/filepath"
    "strings"
)

func ftpConnect(server string, port string) net.Conn {
    conn, err := net.Dial("tcp", server+":"+port)
    if err != nil {
        log.Fatal(err)
    }
    _, err = conn.Read(make([]byte, 1024))
    if err != nil {
        log.Fatal(err)
    }
    return conn
}

func ftpLogin(conn net.Conn, username string, password string) {
    conn.Write([]byte("USER " + username + "
"))
    _, err := conn.Read(make([]byte, 1024))
    if err != nil {
        log.Fatal(err)
    }
    conn.Write([]byte("PASS " + password + "
"))
    _, err = conn.Read(make([]byte, 1024))
    if err != nil {
        log.Fatal(err)
    }
}

func ftpUpload(conn net.Conn, localFilePath string, remoteFileName string) {
    file, err := os.Open(localFilePath)
    if err != nil {
        log.Fatal(err)
    }
    defer file.Close()

    _, err = conn.Write([]byte("TYPE I
"))
    if err != nil {
        log.Fatal(err)
    }

    _, err = conn.Read(make([]byte, 1024))
    if err != nil {
        log.Fatal(err)
    }

    conn.Write([]byte("PASV
"))
    res := make([]byte, 1024)
    _, err = conn.Read(res)
    if err != nil {
        log.Fatal(err)
    }
    ip, port := parsePASVResponse(string(res))

    conn.Write([]byte("STOR " + remoteFileName + "
"))
    dataConn, err := net.Dial("tcp", fmt.Sprintf("%s:%d", ip, port))
    if err != nil {
        log.Fatal(err)
    }

    _, err = conn.Read(make([]byte, 1024))
    if err != nil {
        log.Fatal(err)
    }

    buff := make([]byte, 1024)
    for {
        n, err := file.Read(buff)
        if err != nil && err != io.EOF {
            log.Fatal(err)
        }
        if n == 0 {
            break
        }

        _, err = dataConn.Write(buff[:n])
        if err != nil {
            log.Fatal(err)
        }
    }

    _, err = conn.Read(make([]byte, 1024))
    if err != nil {
        log.Fatal(err)
    }

    dataConn.Close()
}

func parsePASVResponse(response string) (string, int) {
    parts := strings.Split(response, "(")
    addressParts := strings.Split(parts[1], ",")
    ip := strings.Join(addressParts[:4], ".")
    port := (toInt(addressParts[4]) << 8) + toInt(addressParts[5])
    return ip, port
}

func toInt(s string) int {
    var result int
    fmt.Sscanf(s, "%d", &result)
    return result
}

func main() {
    server := "ftp.example.com"
    port := "21"
    username := "username"
    password := "password"
    localFilePath := "/path/to/local/file.txt"
    remoteFileName := "remote_file.txt"

    conn := ftpConnect(server, port)
    ftpLogin(conn, username, password)
    ftpUpload(conn, localFilePath, remoteFileName)

    conn.Write([]byte("QUIT
"))
    _, err := conn.Read(make([]byte, 1024))
    if err != nil {
        log.Fatal(err)
    }
    conn.Close()

    fmt.Println("File uploaded successfully!")
}