Add server section to your Maven settings

Add a server section to your Maven settings (normally in ~/.m2/settings.xml) like this (see https://maven.apache.org/settings.html#Servers for further information):

<settings>
	<servers>
		<server>
			<id>my-server</id>
			<username>your-username</username>
			<password>your-password</password>
		</server>
	</servers>
</settings>

For example, if using Github, the server ID could be github and the username and password would be your Github username and password.

Configure the plugin

Secondly, specify the serverId in the plugin configuration.

<plugin>
	...
	<configuration>
		<serverId>my-server</serverId>
	</configuration>
</plugin>