MJPEG to http jpeg server

main.go

package main

import (
    "bufio"
    "flag"
    "log"
    "net/http"
    "strconv"
    "strings"
    "sync"
)

var JpegData []byte
var mux sync.Mutex

func loadHTTP(url string) {
    resp, err := http.Get(url)
    if err != nil {
        log.Fatalln("Can't connect to HTTP server '" + url + "':\n", err)
    }
    defer resp.Body.Close()
    log.Println("HTTP connected '" + url + "'")

    b := bufio.NewReaderSize(resp.Body, 1*1024*1024)

    for {
        var line []byte
        var err error
        line, _, err = b.ReadLine() // --boundarydonotcross
        if err != nil { log.Fatal("Error Reading: ", err); break }
        line, _, err = b.ReadLine() // Content-Type:image/jpeg
        if err != nil { log.Fatal("Error Reading: ", err); break }
        line, _, err = b.ReadLine() // Content-Length: 22130
        contentLength := string(line)
        if err != nil { log.Fatal("Error Reading: ", err); break }
        line, _, err = b.ReadLine() // empty line
        if err != nil { log.Fatal("Error Reading: ", err); break }

        contentLength = strings.ReplaceAll(contentLength, "Content-Length: ", "")
        contentLen, err := strconv.ParseInt(contentLength, 10, 64)
        if err != nil { log.Fatal("Error parse Content-Length", err); break }

        // println("contentLength: ", contentLen)

        _, err = b.Peek(int(contentLen))
        if err != nil { log.Fatal("Error b.Peek: ", err); break }

        jpegBuf := make([]byte, contentLen)
        n, err := b.Read(jpegBuf)
        if err != nil { log.Fatal("Error b.Peek: ", err); break }
        if n != int(contentLen) { log.Fatalln("n != contentLen", n, contentLen)}

        mux.Lock()
        JpegData = jpegBuf
        mux.Unlock()

        _, _, err = b.ReadLine() // empty line
        if n != int(contentLen) { log.Fatalln("b.ReadLine()", err)}
    }
}

func getJpeg(w http.ResponseWriter, req *http.Request) {
    w.Header().Set("Content-Type", "image/jpeg")
    mux.Lock()
    defer mux.Unlock()
    w.Header().Set("Content-Length", strconv.Itoa(len(JpegData)))
    w.WriteHeader(http.StatusOK)
    // log.Println(len(JpegData))
    w.Write(JpegData)
}

var mjpegUrl = flag.String("mjpeg", "http://192.168.3.21:8080/mjpeg", "mjpeg url")

func main() {

    flag.Parse()

    go loadHTTP(*mjpegUrl)

    http.HandleFunc("/image.jpg", getJpeg)

    err := http.ListenAndServe("0.0.0.0:8090", nil)
    if err != nil { log.Fatalln(err) }
}