func SetFilename(fileName string) {
	logFilename = fileName
}
SetFilename updates filename in which logs will be saved
package logger
import (
	"fmt"
	"log"
	"os"
	"strings"
	"sync"
	"time"
)
var (
	enabledFileLog = true
	logFilename    = "log.txt"
	mu             sync.Mutex
	filter         string
)
func Log(text string) {
	if filter == "" || (filter != "" && strings.Contains(text, filter)) {
		log.Print(text)
		if !enabledFileLog {
			return
		}
		mu.Lock()
		defer mu.Unlock()
		if err := writeToFile(logFilename, text); err != nil {
			log.Println(err)
		}
	}
}
func Logln(v ...interface{}) {
	Log(fmt.Sprintln(v...))
}
func Logf(format string, v ...interface{}) {
	Log(fmt.Sprintf(format, v...))
}