Add ParseURL function for cluster mode (#1924)

* feat: add ParseClusterURL to allow for parsing of redis cluster urls into cluster options

options.go

@@ -255,16 +255,7 @@ func setupTCPConn(u *url.URL) (*Options, error) {
 
 	o.Username, o.Password = getUserPassword(u)
 
-	h, p, err := net.SplitHostPort(u.Host)
-	if err != nil {
-		h = u.Host
-	}
-	if h == "" {
-		h = "localhost"
-	}
-	if p == "" {
-		p = "6379"
-	}
+	h, p := getHostPortWithDefaults(u)
 	o.Addr = net.JoinHostPort(h, p)
 
 	f := strings.FieldsFunc(u.Path, func(r rune) bool {
@@ -274,6 +265,7 @@ func setupTCPConn(u *url.URL) (*Options, error) {
 	case 0:
 		o.DB = 0
 	case 1:
+		var err error
 		if o.DB, err = strconv.Atoi(f[0]); err != nil {
 			return nil, fmt.Errorf("redis: invalid database number: %q", f[0])
 		}
@@ -291,6 +283,23 @@ func setupTCPConn(u *url.URL) (*Options, error) {
 	return setupConnParams(u, o)
 }
 
+// getHostPortWithDefaults is a helper function that splits the url into
+// a host and a port. If the host is missing, it defaults to localhost
+// and if the port is missing, it defaults to 6379.
+func getHostPortWithDefaults(u *url.URL) (string, string) {
+	host, port, err := net.SplitHostPort(u.Host)
+	if err != nil {
+		host = u.Host
+	}
+	if host == "" {
+		host = "localhost"
+	}
+	if port == "" {
+		port = "6379"
+	}
+	return host, port
+}
+
 func setupUnixConn(u *url.URL) (*Options, error) {
 	o := &Options{
 		Network: "unix",
@@ -322,6 +331,12 @@ func (o *queryOptions) string(name string) string {
 	return vs[len(vs)-1]
 }
 
+func (o *queryOptions) strings(name string) []string {
+	vs := o.q[name]
+	delete(o.q, name)
+	return vs
+}
+
 func (o *queryOptions) int(name string) int {
 	s := o.string(name)
 	if s == "" {