Timeout while waiting for emulator to startup

I'm try to run this spring android application: http://ift.tt/1DTPG1w I'm trying to run the Client.When I execute this command, mvn clean package, i get BUILD SUCCESS.

When I execute this command,mvn android:emulator-start I get the following error:

Failed to execute goal com.jayway.maven.plugins.android.generation2:android-maven-plugin:3.9.0-rc.1:emulator-start (default-cli) on project spring-android-showcase-client: MojoExecutionException: Timeout while waiting for emulator to startup.

Anyone can help how to solve this?