golang中server.GracefulStop（）的行为

I have a gRPC server, and I have implemented graceful shutdown of my gRPC server something like this

fun main() {
    //Some code
    term := make(chan os.Signal)
    go func() {
            if err := grpcServer.Serve(lis); err != nil {
                term <- syscall.SIGINT
            }
        }()

    signal.Notify(term, syscall.SIGTERM, syscall.SIGINT)
    <-term
    server.GracefulStop()
    closeDbConnections()
}

This works fine. If instead I write the grpcServer.Serve() logic in main goroutine and instead put the shutdown handler logic into another goroutine, statements after server.GracefulStop() usually do not execute. Some DbConnections are closed, if closeDbConnections() is executed at all.

server.GracefulStop() is a blocking call. Definitely grpcServer.Serve() finishes before server.GracefulStop() completes. So, how long does main goroutine take to stop after this call returns?

The problematic code

func main() {
    term := make(chan os.Signal)
    go func() {
        signal.Notify(term, syscall.SIGTERM, syscall.SIGINT)
        <-term
        server.GracefulStop()
        closeDbConnections()
    }()
    if err := grpcServer.Serve(lis); err != nil {
        term <- syscall.SIGINT
    }
}

This case does not work as expected. After server.GracefulStop() is done, closeDbConnections() may or may not run (usually does not run to completion). I was testing the later case by sending SIGINT by hitting Ctrl-C from my terminal.

Can someone please explain this behavior?

I'm not sure about your question (please clarify it), but I would suggest you to refactor your main in this way:

func main() {

   // ...

   errChan := make(chan error)
   stopChan := make(chan os.Signal)

   // bind OS events to the signal channel
   signal.Notify(stopChan, syscall.SIGTERM, syscall.SIGINT)

   // run blocking call in a separate goroutine, report errors via channel
   go func() {
        if err := grpcServer.Serve(lis); err != nil {
            errChan <- err
        }
    }()

   // terminate your environment gracefully before leaving main function
   defer func() {
      server.GracefulStop()
      closeDbConnections()
   }()

   // block until either OS signal, or server fatal error
   select {
      case err := <-errChan:
          log.Printf("Fatal error: %v
", err) 
      case <-stopChan:
   }

I don't think it's a good idea to mix system events and server errors, like you do in your example: in case if Serve fails, you just ignore the error and emit system event, which actually didn't happen. Try another approach when there are two transports (channels) for two different kind of event that cause process termination.