inject the correct method to the multi package

Author: Craig Peterson

providers/dns/dns_providers.go

@@ -34,6 +34,7 @@ import (
 	"github.com/xenolf/lego/providers/dns/lightsail"
 	"github.com/xenolf/lego/providers/dns/linode"
 	"github.com/xenolf/lego/providers/dns/linodev4"
+	"github.com/xenolf/lego/providers/dns/multi"
 	"github.com/xenolf/lego/providers/dns/mydnsjp"
 	"github.com/xenolf/lego/providers/dns/namecheap"
 	"github.com/xenolf/lego/providers/dns/namedotcom"
@@ -120,6 +121,8 @@ func NewDNSChallengeProviderByName(name string) (acme.ChallengeProvider, error)
 		return linodev4.NewDNSProvider()
 	case "manual":
 		return acme.NewDNSProviderManual()
+	case "multi":
+		return multi.New()
 	case "mydnsjp":
 		return mydnsjp.NewDNSProvider()
 	case "namecheap":
@@ -162,3 +165,7 @@ func NewDNSChallengeProviderByName(name string) (acme.ChallengeProvider, error)
 		return nil, fmt.Errorf("unrecognised DNS provider: %s", name)
 	}
 }
+
+func init() {
+	multi.NewDNSChallengeProviderByName = NewDNSChallengeProviderByName
+}

providers/dns/multi/config.go

@@ -47,7 +47,7 @@ func getConfig() (*MultiProviderConfig, error) {
 			return nil, err
 		}
 	} else {
-		return nil, fmt.Errorf("'multi' provider requires json config in MULTI_CONFIG or MULTI_CONFIG_PATH")
+		return nil, fmt.Errorf("'multi' provider requires json config in MULTI_CONFIG or MULTI_CONFIG_FILE")
 	}
 	cfg := &MultiProviderConfig{}
 	if err = json.Unmarshal(rawJSON, cfg); err != nil {

providers/dns/multi/multi.go

@@ -1,4 +1,4 @@
-// package multi implements a dynamic challenge provider that can select different dns providers for different domains,
+// Package multi implements a dynamic challenge provider that can select different dns providers for different domains,
 // and even multiple distinct dns providers and accounts for each individual domain. This can be useful if:
 //
 // - Multiple dns providers are used for active-active redundant dns service
@@ -11,10 +11,10 @@
 //    "Providers": {
 //      "cloudflare": {
 //        "CLOUDFLARE_EMAIL": "[email protected]",
-//        "CLOUDFLARE_API_KEY": "123qwerty"
+//        "CLOUDFLARE_API_KEY": "123qwerty..."
 //      },
 //      "digitalocean":{
-//        "DO_AUTH_TOKEN": "456uiop"
+//        "DO_AUTH_TOKEN": "456uiop..."
 //      }
 //    }
 //    "Domains": {