Merge pull request #6 from gostalt/mx-email-validator

enable a timeout to be passed to MXEmail validator

rule.go

@@ -1,6 +1,7 @@
 package validate
 
 import (
+	"context"
 	"fmt"
 	"net"
 	"net/http"
@@ -162,15 +163,23 @@ var NotRegex CheckFunc = func(r *http.Request, param string, o Options) error {
 // MXEmail looks up the MX Records on a domain to check if a record exists. If
 // an MX record exists, it is likely that the email address is real. This is
 // smarter than just checking if an email address fits a certain format.
-var MXEmail CheckFunc = func(r *http.Request, param string, _ Options) error {
+var MXEmail CheckFunc = func(r *http.Request, param string, o Options) error {
 	if err := Email(r, param, nil); err != nil {
 		return err
 	}
 
+	timeout, ok := o["timeout"].(int)
+	if !ok {
+		timeout = 5
+	}
+
 	parts := strings.Split(r.Form.Get(param), "@")
 	domain := parts[len(parts)-1]
 
-	records, err := net.LookupMX(domain)
+	rsv := net.Resolver{}
+	ctx, cancel := context.WithTimeout(r.Context(), time.Duration(timeout)*time.Second)
+	defer cancel()
+	records, err := rsv.LookupMX(ctx, domain)
 	if err != nil {
 		return fmt.Errorf("failed to look up MX records for %s", param)
 	}

rule_test.go

@@ -75,7 +75,14 @@ func TestRules(t *testing.T) {
 			MXEmail,
 			[]string{"[email protected]", "[email protected]"},
 			[]string{"me@[email protected]", "juststring", "me@[email protected]"},
-			nil,
+			Options{"timeout": 10},
+		},
+		{
+			// MXEmail, but with a short timeout.
+			MXEmail,
+			[]string{}, // No `passable` values, as these should all time out.
+			[]string{"me@[email protected]", "juststring", "me@[email protected]"},
+			Options{"timeout": 1},
 		},
 		{
 			RFC3339,