@SDGGiesbrecht Thank you so much it's much clear now and error is resolved 
BTW i'm very much new to this SPM and i have some more minor issues in my xcode
- I have some 3rd party dependencies which has min deployment target is 8.0 and my target is 12.0, however i'm getting warning like this
The iOS Simulator deployment target 'IPHONEOS_DEPLOYMENT_TARGET' is set to 8.0, but the range of supported deployment target versions is 9.0 to 14.0.99.
- I tried to set default localization into "Base" i don't think this is valid language code and i'm getting warning like this, i have Base.lproj folder is there any way to set "Base" as default localization?
: resource 'Localizable.strings' in target 'ECKit' is missing the default localization 'Base'; the default localization is used as a fallback when no other localization matches
let package = Package(
name: "ECKit",
defaultLocalization: "Base" .....)