What is graceful shutdown and how does it work in Go?

Graceful shutdown is the proper termination of an application, during which it manages to complete current operations, release resources, and close connections correctly before fully stopping.

In Go, graceful shutdown is usually implemented by handling system signals (e.g., SIGINT, SIGTERM). When a signal is received, the application begins the shutdown process:

• Stops accepting new requests.
• Completes processing of current requests or tasks.
• Releases resources (databases, files, connections).
• Shuts down and exits.

Example of implementing graceful shutdown in Go:

package main

import (
    "context"
    "log"
    "net/http"
    "os"
    "os/signal"
    "syscall"
    "time"
)

func main() {
    srv := &http.Server{Addr: ":8080"}

    // Run server in a separate goroutine
    go func() {
        if err := srv.ListenAndServe(); err != nil && err != http.ErrServerClosed {
            log.Fatalf("ListenAndServe(): %v", err)
        }
    }()

    // Create channel to receive signals
    quit := make(chan os.Signal, 1)
    signal.Notify(quit, syscall.SIGINT, syscall.SIGTERM)
    <-quit // wait for signal

    log.Println("Shutting down server...")

    // Create context with timeout for shutdown
    ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
    defer cancel()

    if err := srv.Shutdown(ctx); err != nil {
        log.Fatalf("Server forced to shutdown: %v", err)
    }

    log.Println("Server exiting")
}

Thus, the application terminates correctly without interrupting active connections and operations.