Notify slack user from Jenkins pipeline when build fails - jenkins

Question

I am sending slack notification to a channel from Jenkins pipeline, I have installed Jenkins slack plugin https://plugins.jenkins.io/slack and configured Jenkins slack app to send notification to the channel whenever the build fails or succeeds. Instead of sending just a failure message to slack channel I want to notify the user saying that the build failed.
eg: #user error in deploying following project
I referred this steps from jenkins slack plugin
def userIds = slackUserIdsFromCommitters()
def userIdsString = userIds.collect { "<#$it>" }.join(' ')
post {
// Send the build result to slack channel
success {
slackSend (color:'good', message: "<#$userIds>Successfully deployed")
}
failure {
slackSend (color:'danger', message: "<#$userIds>Error in build ${env.JOB_NAME}")
}
}
I am getting null value for $userIds variable.

Answer 1

If it is still relevant for someone, I did so:
........
}
post {
always {
script {
env.GIT_COMMIT_MSG = sh (script: 'git log -1 --pretty=%B ${GIT_COMMIT} | head -n1', returnStdout: true).stripIndent().trim()
env.GIT_AUTHOR = sh (script: 'git log -1 --pretty=%ae ${GIT_COMMIT} | awk -F "#" \'{print $1}\' | grep -Po "[a-z]{1,}" | head -n1', returnStdout: true).trim()
slackSend(
color: color_slack_msg(),
message: """
*${currentBuild.currentResult}:* Job `${env.JOB_NAME}` build `${env.BUILD_DISPLAY_NAME}` by <#${env.GIT_AUTHOR}>
Build commit: ${GIT_COMMIT}
Last commit message: '${env.GIT_COMMIT_MSG}'
More info at: ${env.BUILD_URL}
Time: ${currentBuild.durationString.minus(' and counting')}
""".stripIndent().trim(),
channel: 'slack-channel',
tokenCredentialId: 'SlackToken'
)
}
cleanWs()
}
}
}
def color_slack_msg() {
switch(currentBuild.currentResult) {
case "SUCCESS":
return "good"
break
case "FAILURE":
case "UNSTABLE":
return "danger"
break
default:
return "warning"
break
}
}
this will work if mail = login in slack

Answer 2

This feature is only available for a bot user in slack, not for a Jenkins bot app.
The bot user which you create should have access to read and write message to the channel.