start a grpc server

grpc.go

type Config struct {
	GrpcPort    int    `config:"default=8080;usage="`
	UseTLS      bool   `config:"default=false;usage="`
	SSLCertFile string `config:"default=ssl.crt;usage=SSL public key file"`
	SSLKeyFile  string `config:"default=ssl.key;usage=SSL private key file"`
}

type Server struct {
	conf                   *Config
	contentProcessorServer *request_processor.ContentProcessorServer
	lis                    *net.Listener
	grpcServer             *grpc.Server
}

func (s *Server) Start() error {
  listenAddress := fmt.Sprintf("localhost:%d", s.conf.GrpcPort)

  lis, err := net.Listen("tcp", listenAddress)

  if err != nil {
    logrus.Errorf("unable to create network listener err=%#v", err)
    return err
  }

  s.lis = lis
  
  logrus.Debugf("listening on %s", listenAddress)

  if !s.conf.UseTLS {
    if err != nil {
      log.Fatalf("failed to listen: %v", err)
      return err
    }
    s.grpcServer = grpc.NewServer()
  } else {
    certFile := s.conf.SSLCertFile
    keyFile := s.conf.SSLKeyFile
    creds, err := credentials.NewServerTLSFromFile(certFile, keyFile)
    if err != nil {
      log.Fatalf("failed to listen: %v", err)
      return err
    }
    s.grpcServer = grpc.NewServer(grpc.Creds(creds))
  }

  pb.RegisterContentProcessorServer(s.grpcServer, s.contentProcessorServer)

  return s.grpcServer.Serve(lis)
}