read fixed byte size from http connection

main.go

package main

import (
	"flag"
	"fmt"
	"log"
	"net/http"
	"os"
)

func main() {
	filename := flag.String("name", "", "please provide a file name")

	flag.Parse()

	if *filename == "" {
		log.Fatal("failed to provide a filename")
	}

	file, err := os.Open(*filename)
	if err != nil {
		log.Fatal(err)
	}

	bufferSize := 930
	buffer := make([]byte, bufferSize)

	n, err := file.Read(buffer)
	if err != nil {
		log.Fatal(err)
	}

	fmt.Println(buffer)

	mimeType := http.DetectContentType(buffer[:n])

	fmt.Println(mimeType)
}