Fix test for lint

.travis.yml

@@ -1,7 +1,6 @@
 language: go
 go:
-  - 1.7.5
-  - 1.8
+  - 1.9
   - tip
 dist: trusty
 sudo: required

cmd/kamimai/cmd_down.go

@@ -42,10 +42,7 @@ func doDownCmd(cmd *Cmd, args ...string) error {
 
 		if len(args) == 0 {
 			// Just one
-			if err := svc.Prev(1); err != nil {
-				return err
-			}
-			return nil
+			return svc.Prev(1)
 		}
 
 		val := cast.Int(args[0])

cmd/kamimai/cmd_up.go

@@ -42,10 +42,7 @@ func doUpCmd(cmd *Cmd, args ...string) error {
 
 		if len(args) == 0 {
 			// All
-			if err := svc.Up(); err != nil {
-				return err
-			}
-			return nil
+			return svc.Up()
 		}
 
 		val := cast.Int(args[0])