Fix lostcancel

[ne-sachirou]

  Error: graceful.go:61:2: lostcancel: the cancel function is not used on all paths (possible context leak) (govet)
  	ctx, cancel := context.WithCancelCause(ctx)
  	^
  Error: graceful.go:75:3: lostcancel: this return statement may be reached without using the cancel var defined on line 61 (govet)
  		return errors.Join(errors.New("failed to start servers"), err)
  		^