write a newline

Author: JoeWang1127

java-sdk-logging/log4j2-extension/src/main/java/com/google/cloud/sdk/logging/SDKLoggingJsonLayout.java

@@ -85,7 +85,7 @@ public String toSerializable(LogEvent event) {
       }
     }
 
-    return gson.toJson(jsonMap);
+    return String.format("%s\n", gson.toJson(jsonMap));
   }
 
   private void extractNonMdc(LogEvent event, Map<String, Object> jsonMap) {

java-sdk-logging/log4j2-extension/src/test/java/com/google/cloud/sdk/logging/SDKLoggingJsonLayoutTest.java

@@ -66,7 +66,7 @@ void init() {
   @Test
   void testToSerializableContainsNonMdcContents() {
     assertEquals(
-        "{\"timestamp\":10000,\"level\":\"DEBUG\",\"logger_name\":\"com.example.Example\",\"message\":\"example message\"}",
+        "{\"timestamp\":10000,\"level\":\"DEBUG\",\"logger_name\":\"com.example.Example\",\"message\":\"example message\"}\n",
         sdkLoggingJsonLayout.toSerializable(logEvent));
   }
 
@@ -89,7 +89,7 @@ void testToSerializableInvalidJsonValueWriteString() {
     // the last colon is invalid.
     mdcMap.put("example key", "{key:value,jsonKey:{nestedKey:nestedValue,}}");
     assertEquals(
-        "{\"timestamp\":10000,\"level\":\"DEBUG\",\"logger_name\":\"com.example.Example\",\"message\":\"example message\",\"example key\":\"{key:value,jsonKey:{nestedKey:nestedValue,}}\"}",
+        "{\"timestamp\":10000,\"level\":\"DEBUG\",\"logger_name\":\"com.example.Example\",\"message\":\"example message\",\"example key\":\"{key:value,jsonKey:{nestedKey:nestedValue,}}\"}\n",
         sdkLoggingJsonLayout.toSerializable(logEvent));
   }
 
@@ -99,7 +99,7 @@ void testToSerializableValidJsonValueWriteJson() {
     mdcMap.put("example key", "{key:value,jsonKey:{nestedKey:nestedValue}}");
     String log = sdkLoggingJsonLayout.toSerializable(logEvent);
     assertEquals(
-        "{\"timestamp\":10000,\"level\":\"DEBUG\",\"logger_name\":\"com.example.Example\",\"message\":\"example message\",\"example key\":{\"key\":\"value\",\"jsonKey\":{\"nestedKey\":\"nestedValue\"}}}",
+        "{\"timestamp\":10000,\"level\":\"DEBUG\",\"logger_name\":\"com.example.Example\",\"message\":\"example message\",\"example key\":{\"key\":\"value\",\"jsonKey\":{\"nestedKey\":\"nestedValue\"}}}\n",
         log);
     assertDoesNotThrow(() -> JsonParser.parseString(log));
   }