func CheckMails(mails []string) []string {
    var existingMails []string
    fmt.Printf("!!!!!!!!!!!!!!STARTING!!!!!!!!!!!! %s nnn", mails[1])
    for i := 0; i < len(mails); i++ {
        err := validateHost(mails[i])
        if err != nil {
            fmt.Printf("Error validating host. %s", err)
        }
        smtpErr, ok := err.(checkmail.SmtpError)
        if ok {
            fmt.Printf("Code: %s, Msg: %s", smtpErr.Code(), smtpErr)
            if smtpErr.Code() == "dia" {
                break
            }
        } else {
            fmt.Println("Email exists")
            existingMails = append(existingMails, mails[i])
        }
    }
    fmt.Printf("!!!!!!!!!!!!!!ENDING!!!!!!!!!!!! %s nnn", mails[1])
    return existingMails
}

func validateHost(email string) error {
    _, host := split(email)
    mx, err := net.LookupMX(host)
    if err != nil {
        fmt.Printf("Error, UnresolvableHost! %s", err)
    }

    client, err := smtp.Dial(fmt.Sprintf("%s:%d", mx[0].Host, 25))
    //  fmt.Println(client)
    defer client.Close()
    if err != nil {
        //fmt.Println(client)
        //log.Fatalln(err)
        fmt.Printf("SmtpError! %s n", err)
    }

    t := time.AfterFunc(forceDisconnectAfter, func() { client.Close() })
    defer t.Stop()

    // t := NewTimer(10, func() { client.Close() })
    // defer t.Stop()

    err = client.Hello("checkmail.me")
    //err = client.Hello("gmail.com")
    //  fmt.Println(client)
    if err != nil {
        //log.Fatalln(err)
        fmt.Printf("client.Hello SmtpError! %s n", err)
    }

    err = client.Mail("lansome-cowboy@gmail.com")
    if err != nil {
        fmt.Printf("client.MailSmtpError! %s n", err)
    }
    err = client.Rcpt(email)
    if err != nil {
        fmt.Printf("client.Rcpt SmtpError! %s n", err)
    }
    return nil
}

// CheckMailsWithExpectedInterval want to get expectected number of seconds which you are ready to wait while
// the mail trys to be validated (this time is for ONE mail, slice could have a lot of mails to check)
// and slice of mails which should be validated
func CheckMailsWithExpectedInterval(expectedSec int, mails []string) (ok bool, existingMails []string) {
    done := make(chan struct{})
    t1 := time.Now()
    var eMails []string
    go func() {
        eMails = CheckMails(mails)
        close(done)
    }()

    select {
    case <-done:
        if len(eMails) > 1 {
            ok = false
        } else {
            ok = true
            existingMails = eMails
        }
    case <-time.After(time.Duration(expectedSec) * time.Second):
    }

    fmt.Printf("nTime since:")
    fmt.Println(time.Since(t1))
    return ok, existingMails
}

func split(email string) (account, host string) {
    i := strings.LastIndexByte(email, '@')
    account = email[:i]
    host = email[i+1:]
    return
}

const forceDisconnectAfter = time.Second * 10

email1 := []string{
        "andreasId@fromatob.com",
        "Andreas.Wolff@fromatob.com",
        "AndreasWolff@fromatob.com",
        "Wolff.Andreas@fromatob.com",
        "WolffAndreas@fromatob.com",
        "Andreas@fromatob.com,Wolff@fromatob.com",
        "A.Wolff@fromatob.com",
        "AWolff@fromatob.com",
        "Andreas.W@fromatob.com",
        "AndreasW@fromatob.com",
        "Wolff.A@fromatob.com",
        "WolffA@fromatob.com",
        "W.Andreas@fromatob.com",
        "WAndreas@fromatob.com",
    }

panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x0 pc=0x84fefa]
goroutine 260 [running]:
net/smtp.(*Client).Close(0x0, 0x0, 0x0)
    /usr/lib/go-1.10/src/net/smtp/smtp.go:76 +0x2a
panic(0x90a360, 0xb94ae0)
    /usr/lib/go-1.10/src/runtime/panic.go:502 +0x24a
net/smtp.(*Client).Hello(0x0, 0x97d912, 0x9, 0x0, 0x0)
    /usr/lib/go-1.10/src/net/smtp/smtp.go:100 +0x78
magictool/mailchecker.validateHost(0xc4204c7020, 0x23, 0x0, 0x0)
    /home/username/go/src/magictool/mailchecker/mailchecker.go:115 +0x749
magictool/mailchecker.CheckMails(0xc4201c0000, 0xf, 0xf, 0x0, 0x0, 0x0)
    /home/username/go/src/magictool/mailchecker/mailchecker.go:20 +0x1d1
magictool/mailchecker.CheckMailsWithExpectedInterval.func1(0xc4201c0000, 0xf, 0xf, 0xc42038f5c0, 0xc4203b7ec0)
    /home/username/go/src/magictool/mailchecker/mailchecker.go:49 +0x3f
created by magictool/mailchecker.CheckMailsWithExpectedInterval
    /home/username/go/src/magictool/mailchecker/mailchecker.go:48 +0x12c