[Vendor] update go-swagger v0.21.0 -> v0.25.0 (#12670)

* Update go-swagger

* vendor

vendor/github.com/go-openapi/spec/expander.go

@@ -200,11 +200,11 @@ func ExpandSpec(spec *Swagger, options *ExpandOptions) error {
 	return nil
 }
 
+const rootBase = "root"
 // baseForRoot loads in the cache the root document and produces a fake "root" base path entry
 // for further $ref resolution
 func baseForRoot(root interface{}, cache ResolutionCache) string {
 	// cache the root document to resolve $ref's
-	const rootBase = "root"
 	if root != nil {
 		base, _ := absPath(rootBase)
 		normalizedBase := normalizeAbsPath(base)
@@ -452,11 +452,12 @@ func expandPathItem(pathItem *PathItem, resolver *schemaLoader, basePath string)
 		return err
 	}
 	if pathItem.Ref.String() != "" {
-		var err error
-		resolver, err = resolver.transitiveResolver(basePath, pathItem.Ref)
-		if resolver.shouldStopOnError(err) {
+		transitiveResolver, err := resolver.transitiveResolver(basePath, pathItem.Ref)
+		if transitiveResolver.shouldStopOnError(err) {
 			return err
 		}
+		basePath = transitiveResolver.updateBasePath(resolver, basePath)
+		resolver = transitiveResolver
 	}
 	pathItem.Ref = Ref{}