Getting error on CI with Xamarin and jenkins

Hi,

I am doing CI for Xamarin.iOS app using Xamarin and jenkins. I have installed and jenkins and configured as mentioned in Xamarin https://developer.xamarin.com/guides/cross-platform/ci/jenkins_walkthrough/

Getting the below build error when build in jenkins

/Library/Frameworks/Mono.framework/Versions/4.0.5/lib/mono/4.5/Microsoft.Common.targets : warning: Reference 'Xamarin.Forms.Core' not resolved

/Library/Frameworks/Mono.framework/Versions/4.0.5/lib/mono/4.5/Microsoft.Common.targets : warning: Reference 'Xamarin.Forms.Xaml' not resolved
/Users/admin/.jenkins/jobs/MyProject/workspace/HelloWorld/HelloWorld.cs(3,7) : error CS0246: The type or namespace name

Xamarin' could not be found. Are you missing an assembly reference?
/Users/admin/.jenkins/jobs/MyProject/workspace/HelloWorld/MainPage.xaml.cs(4,7) : error CS0246: The type or namespace name

Xamarin' could not be found. Are you missing an assembly reference?
/Users/admin/.jenkins/jobs/MyProject/workspace/HelloWorld/HelloWorld.cs(7,21) : error CS0246: The type or namespace name

Application' could not be found. Are you missing an assembly reference?
/Users/admin/.jenkins/jobs/MyProject/workspace/HelloWorld/MainPage.xaml.cs(8,34) : error CS0246: The type or namespace name

ContentPage' could not be found. Are you missing an assembly reference?
/Users/admin/.jenkins/jobs/MyProject/workspace/HelloWorld/HelloWorld.cs(14,27) : error CS0115:

HelloWorld.App.OnStart()' is marked as an override but no suitable method found to override
/Users/admin/.jenkins/jobs/MyProject/workspace/HelloWorld/HelloWorld.cs(19,27) : error CS0115:

HelloWorld.App.OnSleep()' is marked as an override but no suitable method found to override
/Users/admin/.jenkins/jobs/MyProject/workspace/HelloWorld/HelloWorld.cs(24,27) : error CS0115: `HelloWorld.App.OnResume()' is marked as an override but no suitable method found to override

Build failed

Need help on this