Use umask 0077 across the process in order to have the created files readable...

Use umask 0077 across the process in order to have the created files readable only by the acme-dns user (#102)

main.go

@@ -7,6 +7,7 @@ import (
 	stdlog "log"
 	"net/http"
 	"os"
+	"syscall"
 
 	"github.com/julienschmidt/httprouter"
 	"github.com/rs/cors"
@@ -15,6 +16,8 @@ import (
 )
 
 func main() {
+	// Created files are not world writable
+	syscall.Umask(0077)
 	// Read global config
 	var err error
 	if fileIsAccessible("/etc/acme-dns/config.cfg") {