code: func IsStdin(ctx context.Context) bool {
  	bv, ok := ctx.Value(ctxKeyStdin).(bool)
  	if !ok {
  		return false
  	}
  	return bv
  }
docs: // IsStdin returns the value of stdin, i.e. if it's true some data is being
  // piped to stdin. If not set it returns the default value (false)