Certificate fetcher in Go

fetch.go

package main

import "crypto/tls"
import "crypto/sha1"
import "crypto/x509"
import "fmt"
import "encoding/pem"
import "os"
import "time"
import "bufio"
import "strings"
import "net"


func storeCertificate(cert *x509.Certificate) {
    hash := sha1.New()
    hash.Write(cert.Raw)
    filename := fmt.Sprintf("%X", hash.Sum(nil))
    if _, err := os.Stat(filename); os.IsNotExist(err) {
        f, _ := os.Create(filename)
        defer f.Close()
        block := &pem.Block{"CERTIFICATE", nil, cert.Raw}
        fmt.Println("\x1b[32;1madded", filename, "\x1b[0m")
        pem.Encode(f, block)
    }
}


func analyzeDomain(domain string) {
    fmt.Println("analyzing", domain)
    dialer := net.Dialer{}
    dialer.Timeout = 10 * time.Second
    conn, err := tls.DialWithDialer(&dialer, "tcp", domain, &tls.Config{
        InsecureSkipVerify: true,
    })
    if err != nil {
        fmt.Println(fmt.Sprintf("\x1b[31;1mfailed to connect to %s", domain), err, "\x1b[0m")
        return
    }
    defer conn.Close()
    for _, cert := range conn.ConnectionState().PeerCertificates {
        storeCertificate(cert)
    }
}


func analyzeDomains(queue chan string) {
    for {
        domain := <-queue
        analyzeDomain(domain)
    }
}


func main () {
    cs := make(chan string)
    for i := 0; i < 80; i++ {
        go analyzeDomains(cs)
    }
    scanner := bufio.NewScanner(os.Stdin)
    for scanner.Scan() {
        line := scanner.Text()
        if ! strings.Contains(line, ":") {
            line = line + ":443"
        }
        cs <- line
    }
    time.Sleep(2 * time.Second)
}