Add checkout and build step

vars/build.groovy

+def call(String buildDirectory) {
+    stage('Build') {
+        dir(buildDirectory) {
+            sh 'mvn clean install'
+        }
+    }
+}
\ No newline at end of file

vars/checkStatus.groovy → vars/checkout.groovy

 #!/usr/bin/env groovy
 
 def call(body) {
-    echo "Check status"
-
-    (1..3).each {
-        echo "Number: " + it
+    stage('Checkout SCM') {
+        steps {
+            checkout scm
+        }
     }
-
-    currentBuild.result = 'SUCCESS' //FAILURE to fail
     return this
 }

vars/hello.groovy

-def hello() {
-    echo "hello() called!"
-}
\ No newline at end of file