Use concrete class for AvroCoder compatibility (#465)

Chen Zhiling · web-flow · commit 951a5b5d4f0d · 2020-02-07T13:11:49.000+08:00
diff --git a/sdk/java/src/main/java/com/gojek/feast/Row.java b/sdk/java/src/main/java/com/gojek/feast/Row.java
@@ -31,7 +31,7 @@
 @SuppressWarnings("UnusedReturnValue")
 public class Row {
   private Timestamp entity_timestamp;
-  private Map<String, Value> fields;
+  private HashMap<String, Value> fields;
 
   public static Row create() {
     Row row = new Row();
