load groovy file/lib into Jenkinsfile

Jenkinsfile

node(label) {
  step([$class: 'WsCleanup'])

  sh "wget -O ./pipeline.lib.groovy https://github.com/<url>/pipeline.lib.groovy"

  def pipelineLib = load 'pipeline.lib.groovy'
  pipelineLib.checkoutSource(<your params>)
  pipelineLib.buildProject(<your params>)
  pipelineLib.publishArtifacts(<your params>)
  pipelineLib.archiveArtifacts(<your params>)
}

pipeline.lib.groovy

public checkoutSource(<your params>) {
  // do something
}

public buildProject(<your params>) {
  // do something
}

public publishArtifacts(<your params>) {
  // do something
}

public archiveArtifacts(<your params>) {
  // do something
}

return this