When I added firebase to my project then I got this error
/Users/mac/Projects/mobile/texknoter/ios/Pods/Firebase/CoreOnly/Sources/module.modulemap:1:8: error: redefinition of module 'Firebase'
module Firebase { ^ /Users/mac/Library/Developer/Xcode/DerivedData/Texknoter-gpxrhbzgwlqljfgxhvvsyxmpufnv/SourcePackages/checkouts/firebase-ios-sdk/CoreOnly/Sources/module.modulemap:1:8: note: previously defined here
module Firebase { ^ /Users/mac/Library/Developer/Xcode/DerivedData/Texknoter-gpxrhbzgwlqljfgxhvvsyxmpufnv/Build/Intermediates.noindex/Texknoter.build/Debug-iphonesimulator/Texknoter.build/Objects-normal/x86_64/AppDelegate.dia:1:1: warning: Could not read serialized diagnostics file: error("Failed to open diagnostics file") (in target 'Texknoter' from project 'Texknoter')