Support custom DNS resolvers for Let's Encrypt.

types/dns_resolvers.go

@@ -0,0 +1,44 @@
+package types
+
+import (
+	"fmt"
+	"strings"
+)
+
+// DNSResolvers is a list of DNSes that we will try to resolve the challenged FQDN against
+type DNSResolvers []string
+
+// String is the method to format the flag's value, part of the flag.Value interface.
+// The String method's output will be used in diagnostics.
+func (r *DNSResolvers) String() string {
+	return strings.Join(*r, ",")
+}
+
+// Set is the method to set the flag value, part of the flag.Value interface.
+// Set's argument is a string to be parsed to set the flag.
+// It's a comma-separated list, so we split it.
+func (r *DNSResolvers) Set(value string) error {
+	entryPoints := strings.Split(value, ",")
+	if len(entryPoints) == 0 {
+		return fmt.Errorf("wrong DNSResolvers format: %s", value)
+	}
+	for _, entryPoint := range entryPoints {
+		*r = append(*r, entryPoint)
+	}
+	return nil
+}
+
+// Get return the DNSResolvers list
+func (r *DNSResolvers) Get() interface{} {
+	return *r
+}
+
+// SetValue sets the DNSResolvers list
+func (r *DNSResolvers) SetValue(val interface{}) {
+	*r = val.(DNSResolvers)
+}
+
+// Type is type of the struct
+func (r *DNSResolvers) Type() string {
+	return "dnsresolvers"
+}