vspd: Remove shutdownRequestChannel.

The removal of the requestShutdown function in a previous commit means
that the shutdownRequestChannel is no longer needed, so this commit
removes it.

cmd/vspd/main.go

@@ -107,7 +107,7 @@ func run() int {
 	var shutdownWg sync.WaitGroup
 
 	// Create a context that is canceled when a shutdown request is received
-	// through an interrupt signal.
+	// through an interrupt signal such as SIGINT (Ctrl+C).
 	ctx := shutdownListener(log)
 
 	// Start the webapi server.

cmd/vspd/signal.go

@@ -13,10 +13,6 @@ import (
 	"github.com/decred/slog"
 )
 
-// shutdownRequestChannel is used to initiate shutdown from one of the
-// subsystems using the same code paths as when an interrupt signal is received.
-var shutdownRequestChannel = make(chan struct{})
-
 // interruptSignals defines the signals that are handled to do a clean shutdown.
 // Conditional compilation is used to also include SIGTERM and SIGHUP on Unix.
 var interruptSignals = []os.Signal{os.Interrupt}
@@ -31,24 +27,16 @@ func shutdownListener(log slog.Logger) context.Context {
 		signal.Notify(interruptChannel, interruptSignals...)
 
 		// Listen for the initial shutdown signal.
-		select {
+		sig := <-interruptChannel
-		case sig := <-interruptChannel:
 		log.Infof("Received signal (%s). Shutting down...", sig)
-		case <-shutdownRequestChannel:
-			log.Info("Shutdown requested. Shutting down...")
-		}
 
 		cancel()
 
 		// Listen for any more shutdown request and display a message so the
 		// user knows the shutdown is in progress and the process is not hung.
 		for {
-			select {
+			sig := <-interruptChannel
-			case sig := <-interruptChannel:
 			log.Infof("Received signal (%s). Already shutting down...", sig)
-			case <-shutdownRequestChannel:
-				log.Info("Shutdown requested. Already shutting down...")
-			}
 		}
 	}()
 	return ctx