gistfile1.txt

pipeline {
    environment {
    LANG = "C.UTF-8"
    }
    agent {
        docker {  
            image 'centos:7' 
            args '-p 2222:22 -v --privileged '
        }
    }
    stages { 
      stage("PushToGitHub") {
        steps { 
          sh """yum install -y git 
          echo 'root:test' | chpasswd
          git config --global user.email "example@example.com"
          git config --global user.name "Automation"
          git config --global push.default simple
          """
         sshagent (credentials:['plupu-github']) {
            sh """
              git checkout staging
              git pull --rebase
            """
            }
          }
        }
      }
    post { 
        failure {
                input 'Build failed, SSH is open at port: 2222'
        }
    }
}

gistfile2.txt

[Pipeline] sshagent
[ssh-agent] Using credentials git (plupu-github)
[ssh-agent] Looking for ssh-agent implementation...
[ssh-agent]   Exec ssh-agent (binary ssh-agent on a remote machine)
$ docker exec 8dc329784a3517c27eff3b9bcefec4cf1cc296d6c13ff26fdcd417f669df1e5f ssh-agent
SSH_AUTH_SOCK=/tmp/ssh-BxsIqboprJDx/agent.104
SSH_AGENT_PID=109
Running ssh-add (command line suppressed)
Identity added: /var/lib/jenkins/workspace/web-staging@tmp/private_key_4159778290407912291.key (/var/lib/jenkins/workspace/web-staging@tmp/private_key_4159778290407912291.key)
[ssh-agent] Started.
[Pipeline] {
[Pipeline] sh
+ git checkout staging
Previous HEAD position was eee3853... Amended
Switched to branch 'staging'
+ git pull --rebase
Host key verification failed.
fatal: Could not read from remote repository.

Please make sure you have the correct access rights
and the repository exists.
[Pipeline] }
$ docker exec --env ******** --env ******** 8dc329784a3517c27eff3b9bcefec4cf1cc296d6c13ff26fdcd417f669df1e5f ssh-agent -k
unset SSH_AUTH_SOCK;
unset SSH_AGENT_PID;
echo Agent pid 109 killed;
[ssh-agent] Stopped.
[Pipeline] // sshagent
[Pipeline] }
[Pipeline] // stage
[Pipeline] stage
[Pipeline] { (Declarative: Post Actions)
[Pipeline] input
Build failed, SSH is open at port: 2222