code: func WithNotaryServer(notaryURL string) func(*icmd.Cmd) {
  	return func(cmd *icmd.Cmd) {
  		env := append(os.Environ(),
  			"DOCKER_CONTENT_TRUST_SERVER="+notaryURL,
  		)
  		cmd.Env = append(cmd.Env, env...)
  	}
  }
docs: //WithNotaryServer sets the location of the notary server