cmd/mbf: test cure all via daemon

This is the daemon equivalent of CureAll in internal/rosa.

Signed-off-by: Ophestra <cat@gensokyo.uk>

cmd/mbf/main.go

@@ -136,7 +136,17 @@ func main() {
 	c.NewCommand(
 		"checksum", "Compute checksum of data read from standard input",
 		func([]string) error {
-			go func() { <-ctx.Done(); os.Exit(1) }()
+			done := make(chan struct{})
+			defer close(done)
+			go func() {
+				select {
+				case <-ctx.Done():
+					os.Exit(1)
+				case <-done:
+					return
+				}
+			}()
+
 			h := sha512.New384()
 			if _, err := io.Copy(h, os.Stdin); err != nil {
 				return err