[StackOverflow/go] Go RPC streaming send not working properly when optional values not provided

### ROOT CAUSE The issue arises because the server-side code does not handle the absence of an optional field in the streaming RPC message. When an optional field is not provided, the server expects it to be present, leading to a panic or incorrect behavior. This is due to improper validation or handling of the optional field in the server's processing logic. ### CODE FIX Modify the server-side code to explicitly check for the absence of the optional field and handle it appropriately. Here's an example fix using Go: ```go // In the server method handler, check for the optional field's absence func (s *server) streamMethod(stream pb.MyService_StreamMethodServer) error { for { req, err := awaitMessage(stream) if err != nil { break } // Check if the optional field is set if req.OptionalField == nil { // Handle absence (e.g., use default, log, or skip) log.Printf("Optional field is not set in message: %+v", req) // Optionally, set a default value req.OptionalField = proto.Int32(0) } // Process the message processMessage(req) } return nil } ``` **Explanation:** - The server checks if the optional field (`OptionalField`) is `nil` (absent) in each received message. - If absent, it logs a warning and sets a default value to avoid panics or undefined behavior. - Adjust the logic based on your specific requirements (e.g., skip the message, use a default, or return an error). This ensures the server gracefully handles missing optional fields during streaming RPC.