Clean up uses of deprecated io/ioutil.
diff --git a/shell_test.go b/shell_test.go
index 38ee1a8..c6ef732 100644
--- a/shell_test.go
+++ b/shell_test.go
@@ -3,7 +3,6 @@
 import (
 	"fmt"
 	"io"
-	"io/ioutil"
 	"log"
 	"strings"
 	"testing"
@@ -195,7 +194,7 @@
 			break
 		}
 	}
-	rest, err := ioutil.ReadAll(s.Rest())
+	rest, err := io.ReadAll(s.Rest())
 	if err != nil {
 		log.Fatal(err)
 	}