Merge pull request #3018 from swagger-api/ticket-3016

refs #3016 - synchronized OpenApiContextLocator

modules/swagger-integration/src/main/java/io/swagger/v3/oas/integration/OpenApiContextLocator.java

@@ -14,7 +14,7 @@ public class OpenApiContextLocator {
     private OpenApiContextLocator() {
     }
 
-    public static OpenApiContextLocator getInstance() {
+    public static synchronized OpenApiContextLocator getInstance() {
         if (instance == null) {
             instance = new OpenApiContextLocator();
         }