func (f *File) ContentType() string {
	mtype := mime.TypeByExtension(filepath.Ext(f.Filename))
	if mtype == "" {
		if strings.HasSuffix(f.Filename, ".webm") {
			return "video/webm; charset=binary"
		}
	}
	return mtype
}
ContentType guesses the mime-type by the file's extension
package types
import (
	"mime"
	"path/filepath"
	"strings"
	"time"
)
type Info struct {
	Keywords  []string  
	Ip        string    
	Random    int64
	TimeStamp time.Time "timestamp,omitempty"
}
type File struct {
	Metadata   Info ",omitempty"
	Md5        string
	ChunkSize  int
	UploadDate time.Time
	Length     uint64
	Filename   string ",omitempty"
}