Golang net/http.DetectContentType() function examples

package net/http

Golang net/http.DetectContentType() function usage examples

Example 1:

 package main

 import (
 "fmt"
 "io/ioutil"
 "log"
 "net/http"
 )

 func main() {
 res, err := http.Get("https://d1ohg4ss876yi2.cloudfront.net/preview/golang.png")
 if err != nil {
 log.Fatal(err)
 }

 unknown, err := ioutil.ReadAll(res.Body)
 res.Body.Close()
 if err != nil {
 log.Fatal(err)
 }

 fileType := http.DetectContentType(unknown)

 fmt.Println("FileType: ", fileType)
 }

Example 2: ( from https://www.socketloop.com/tutorials/golang-how-to-verify-uploaded-file-is-image-or-allowed-file-types )

  package main

  import (
 "fmt"
 "net/http"
 "os"
 "runtime"
  )

  func main() {

 // maximize CPU usage for maximum performance
 runtime.GOMAXPROCS(runtime.NumCPU())

 // open the uploaded file
 file, err := os.Open("./img.png")

 if err != nil {
 fmt.Println(err)
 os.Exit(1)
 }

 buff := make([]byte, 512) // why 512 bytes ? see http://golang.org/pkg/net/http/#DetectContentType
 _, err = file.Read(buff)

 if err != nil {
 fmt.Println(err)
 os.Exit(1)
 }

 filetype := http.DetectContentType(buff)

 fmt.Println(filetype)

 switch filetype {
 case "image/jpeg", "image/jpg":
 fmt.Println(filetype)

 case "image/gif":
 fmt.Println(filetype)

 case "image/png":
 fmt.Println(filetype)

 case "application/pdf": // not image, but application !
 fmt.Println(filetype)
 default:
 fmt.Println("unknown file type uploaded")
 }

  }

Reference :

http://golang.org/pkg/net/http/#DetectContentType