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Cancellation
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| package main | |
| import ( | |
| "context" | |
| "errors" | |
| "fmt" | |
| "log" | |
| "net" | |
| "net/http" | |
| "os" | |
| "os/signal" | |
| "time" | |
| ) | |
| type contextKey string | |
| const ( | |
| ShutdownContextKey = contextKey("shutdown") | |
| ) | |
| func main() { | |
| errCh := make(chan error) | |
| sigCh := make(chan os.Signal) | |
| signal.Notify(sigCh, os.Interrupt) | |
| ctx := context.Background() | |
| shutdownCtx, cancel := context.WithCancel(ctx) | |
| ctx = context.WithValue(ctx, ShutdownContextKey, shutdownCtx) | |
| s := &http.Server{ | |
| Addr: ":8080", | |
| Handler: &Long{}, | |
| BaseContext: func(_ net.Listener) context.Context { return ctx }, | |
| } | |
| s.RegisterOnShutdown(cancel) | |
| go func() { errCh <- s.ListenAndServe() }() | |
| // Main loop | |
| var err error | |
| for err == nil { | |
| select { | |
| case s := <-sigCh: | |
| switch s { | |
| case os.Interrupt: | |
| err = errors.New(s.String()) | |
| } | |
| case err = <-errCh: | |
| } | |
| } | |
| // Shutdown | |
| { | |
| ctx, cancel := context.WithTimeout(context.Background(), 3*time.Second) | |
| if err := s.Shutdown(ctx); err != nil { | |
| log.Printf("error during shutdown: %v", err) | |
| } | |
| cancel() | |
| } | |
| if err != nil { | |
| log.Printf("shutdown: %v", err) | |
| os.Exit(1) | |
| } | |
| os.Exit(0) | |
| } | |
| type Long struct{} | |
| func (Long) ServeHTTP(w http.ResponseWriter, r *http.Request) { | |
| if r.Method != http.MethodGet { | |
| http.Error(w, http.StatusText(http.StatusMethodNotAllowed), http.StatusMethodNotAllowed) | |
| return | |
| } | |
| f, ok := w.(http.Flusher) | |
| if !ok { | |
| http.Error(w, "Streaming events not supported", http.StatusBadRequest) | |
| return | |
| } | |
| w.Header().Set("Content-Type", "text/event-stream") | |
| w.Header().Set("Cache-Control", "no-cache") | |
| w.Header().Set("Transfer-Encoding", "chunked") | |
| ctx := r.Context().Value(ShutdownContextKey).(context.Context) | |
| t := time.NewTicker(time.Second) | |
| defer t.Stop() | |
| for { | |
| f.Flush() | |
| select { | |
| case <-t.C: | |
| fmt.Fprintf(w, "type: ping\n\n") | |
| case <-r.Context().Done(): // Client gone | |
| return | |
| case <-ctx.Done(): // Server shutting down | |
| fmt.Fprintf(w, "type: shutdown\n\n") | |
| f.Flush() | |
| return | |
| } | |
| } | |
| } |
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