add priority option in case some tool has inconsistent issue

config.go

@@ -5,15 +5,21 @@ import (
 	"time"
 )
 
+type UpstreamPriorityGroup struct {
+	Match    string `yaml:"match"`
+	Priority int    `yaml:"priority"`
+}
+
 type UpstreamMatch struct {
 	Match   string `yaml:"match"`
 	Replace string `yaml:"replace"`
 }
 
 type Upstream struct {
-	Server          string        `yaml:"server"`
-	Match           UpstreamMatch `yaml:"match"`
-	AllowedRedirect *string       `yaml:"allowed-redirect"`
+	Server          string                  `yaml:"server"`
+	Match           UpstreamMatch           `yaml:"match"`
+	AllowedRedirect *string                 `yaml:"allowed-redirect"`
+	PriorityGroups  []UpstreamPriorityGroup `yaml:"priority-groups"`
 }
 
 func (upstream Upstream) GetPath(orig string) (string, bool, error) {