The *.pb.go and *_test.go files are not present in the SonarCloud reports but the *mock.go files under the test/mock/ subdirectories are still being reported.
For the sonar.exclusions property we also have some files that use a top level directory and this is excluded correctly so we suspect that the pattern matching for sonar.go.exclusions is not working consistently:
Ann, yes using sonar.exclusions would be an option but sonar.go.exclusions is a valid property. See this screenshot from the language setting in SonarCloud: