code: func FindService(s *pb.FileDescriptorSet, fullName string) (file *pb.FileDescriptorProto, serviceIndex int) {
  	pkg, name := splitFullName(fullName)
  	for _, f := range s.GetFile() {
  		if f.GetPackage() == pkg {
  			if i := FindServiceForFile(f, name); i != -1 {
  				return f, i
  			}
  		}
  	}
  	return nil, -1
  }
docs: // FindService searches for a service by full name.