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/*
GetFileContentType returns the content type of given file by sniffing out fist 512 bytes of the file
Use the net/http package's handy DectectContentType function.
Always returns a valid content-type by returning "application/octet-stream" if no others seemed to match.
It also retruns error, if any.
*/
func GetFileContentType(file *os.File) (string, error) {

	// Only the first 512 bytes are used to sniff the content type.
	buffer := make([]byte, 512)
	_, err := file.Read(buffer)
	if err != nil {
		return "", err
	}

	contentType := http.DetectContentType(buffer)
	return contentType, nil
}