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12-basic-jenkinsfile.md

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+# Building Continuous Delivery (CD) Pipelines
+
+## Writing a basic Jenkinsfile
+
+1. Create a new GitHub repository named `go-on-jenkins`.
+2. Create a new `Jenkinsfile` in the root directory of the repository as well as a simple `main.go` file. The main function just prints "Hello World!". Initialize the project via Go Modules.
+3. Commit the files and push them to the remote repository.
+4. Set up a new pipeline job for this repository in Jenkins.
+5. Install the Jenkins Go plugin.
+6. Configure the latest Go runtime as global tool.
+7. Enhance the `Jenkinsfile` based on the following requirements. The Jenkinsfile should use the declarative syntax.
+    7.1 The job can run on all agents.
+    7.2 The job sets the environment variable `GO111MODULES=on`.
+    7.3 The job uses the Go runtime from the global tool definition.
+    7.4 The job specifies one build stage named "Build". The build stage executes the shell command `go build`.
+
+<details><summary>Show Solution</summary>
+<p>
+
+Create a new job.
+
+![New Job](./images/12-basic-jenkinsfile/new-job.png)
+
+Configure the appropriate SCM.
+
+![Job SCM](./images/12-basic-jenkinsfile/job-scm.png)
+
+Install the Go plugin.
+
+![Go Plugin](./images/12-basic-jenkinsfile/go-plugin.png)
+
+Configure a Go runtime as global tool.
+
+![Go Global Tool](./images/12-basic-jenkinsfile/go-global-tool.png)
+
+The final `Jenkinsfile` looks similar to the solution below.
+
+```groovy
+pipeline {
+    agent any
+    tools {
+        go 'go-1.12'
+    }
+    environment {
+        GO111MODULE = 'on'
+    }
+    stages {
+        stage('Build') {
+            steps {
+                sh 'go build'
+            }
+        }
+    }
+}
+```
+
+A build of the job installs the Go runtime and executes the build step.
+
+![Declarative Pipeline](./images/12-basic-jenkinsfile/declarative-pipeline.png)
+
+</p>
+</details>