How to add an after callback in Gin framework - go

Question

I need to quit the application with os.Exit(0) AFTER HTTP request has finished completely. My application asks another server if it needs an upgrade, so I need to quit for performing a self upgrade with a reboot, but I don't want to break current HTTP request.
When I try to quit in middleware after c.Next() or at the end of handler function, the browser gives error: localhost didn’t send any data.
How this can be done?

Answer 1

As you say, your program is terminating before the HTTP connection completes cleanly - you need to wait for the HTTP transaction to finish and then exit. Fortunately since Go 1.8 http.Server has a Shutdown method that does what you need.
Shutdown gracefully shuts down the server without interrupting any active connections. Shutdown works by first closing all open listeners, then closing all idle connections, and then waiting indefinitely for connections to return to idle and then shut down.
So, the general approach would be:
exitChan := make(chan struct{})
// Get a reference to exitChan to your handlers somehow
h := &http.Server{
// your config
}
go func(){
h.ListenAndServe() // Run server in goroutine so as not to block
}()
<-exitChan // Block on channel
h.Shutdown(nil) // Shutdown cleanly with a timeout of 5 seconds
And then exitChan <- struct{}{} in your handler/middleware when shutdown is required.
See also: How to stop http.ListenAndServe()

Answer 2

You can refer to this example on their github repository:
graceful-shutdown
package main
import (
"context"
"log"
"net/http"
"os"
"os/signal"
"time"
"github.com/gin-gonic/gin"
)
func main() {
router := gin.Default()
router.GET("/", func(c *gin.Context) {
time.Sleep(5 * time.Second)
c.String(http.StatusOK, "Welcome Gin Server")
})
srv := &http.Server{
Addr: ":8080",
Handler: router,
}
go func() {
// service connections
if err := srv.ListenAndServe(); err != nil && err != http.ErrServerClosed {
log.Fatalf("listen: %s\n", err)
}
}()
// Wait for interrupt signal to gracefully shutdown the server with
// a timeout of 5 seconds.
quit := make(chan os.Signal)
signal.Notify(quit, os.Interrupt)
<-quit
log.Println("Shutdown Server ...")
ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
defer cancel()
if err := srv.Shutdown(ctx); err != nil {
log.Fatal("Server Shutdown:", err)
}
log.Println("Server exiting")
}