Don't close m.exitCh just after context cancelletion

The context is used to let the SDK kill its underlying Firecracker
process. Closing the channel has to be happening after the actual
termination of the process.

Signed-off-by: Kazuyoshi Kato <[email protected]>

Author: kzys

machine.go

@@ -516,14 +516,19 @@ func (m *Machine) startVMM(ctx context.Context) error {
 
 		return err
 	}
+
+	// This goroutine is used to kill the process by context cancelletion,
+	// but doesn't tell anyone about that.
 	go func() {
-		select {
-		case <-ctx.Done():
-			m.fatalErr = ctx.Err()
-		case err := <-errCh:
-			m.fatalErr = err
-		}
+		<-ctx.Done()
+		m.stopVMM()
+	}()
 
+	// This goroutine is used to tell clients that the process is stopped
+	// (gracefully or not).
+	go func() {
+		m.fatalErr = <-errCh
+		m.logger.Debugf("closing the exitCh %v", m.fatalErr)
 		close(m.exitCh)
 	}()