fixing bugs in samples

pom.xml

@@ -62,6 +62,11 @@
       <artifactId>httpmime</artifactId>
       <version>4.5.13</version>
     </dependency>
+    <dependency>
+      <groupId>com.google.code.gson</groupId>
+      <artifactId>gson</artifactId>
+      <version>2.8.6</version>
+    </dependency>
     <dependency>
       <groupId>io.reactivex</groupId>
       <artifactId>rxjava</artifactId>