feat: implement update command and add error check for toml key access

cmd/utils/other.go

@@ -44,6 +44,18 @@ func GetEnvy() (*toml.Tree, error) {
 	}
 }
 
+func GetKey(t *toml.Tree, key string) (string, error) {
+	v := t.Get(key)
+	if v == nil {
+		return "", fmt.Errorf("key %v not found", v)
+	}
+	s, ok := v.(string)
+	if !ok {
+		return "", fmt.Errorf("key %q is %T, expected string", key, v)
+	}
+	return s, nil
+}
+
 func WriteEnvy(tree *toml.Tree) error {
 	data, err := tree.Marshal()
 	if err != nil {