Update pom.xml for Release (#261)

Co-authored-by: tsaitsung-han.tht <tsaitsung-han.tht@alibaba-inc.com>

Author: tsunghanjacktsai

pom.xml

@@ -248,17 +248,6 @@
                     <artifactId>coveralls-maven-plugin</artifactId>
                     <version>4.3.0</version>
                 </plugin>
-                <plugin>
-                    <groupId>org.sonatype.plugins</groupId>
-                    <artifactId>nexus-staging-maven-plugin</artifactId>
-                    <version>1.6.3</version>
-                    <extensions>true</extensions>
-                    <configuration>
-                        <serverId>sonatype-nexus-staging</serverId>
-                        <nexusUrl>https://oss.sonatype.org/</nexusUrl>
-                        <autoReleaseAfterClose>true</autoReleaseAfterClose>
-                    </configuration>
-                </plugin>
             </plugins>
         </pluginManagement>
 
@@ -292,6 +281,31 @@
                 <groupId>org.eluder.coveralls</groupId>
                 <artifactId>coveralls-maven-plugin</artifactId>
             </plugin>
+            <plugin>
+                <groupId>org.sonatype.plugins</groupId>
+                <artifactId>nexus-staging-maven-plugin</artifactId>
+                <version>1.6.3</version>
+                <extensions>true</extensions>
+                <configuration>
+                    <serverId>sonatype-nexus-staging</serverId>
+                    <nexusUrl>https://oss.sonatype.org/</nexusUrl>
+                    <autoReleaseAfterClose>true</autoReleaseAfterClose>
+                </configuration>
+            </plugin>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-gpg-plugin</artifactId>
+                <version>1.6</version>
+                <executions>
+                    <execution>
+                        <id>sign-artifacts</id>
+                        <phase>verify</phase>
+                        <goals>
+                            <goal>sign</goal>
+                        </goals>
+                    </execution>
+                </executions>
+            </plugin>
         </plugins>
     </build>