anchor.diff:          name = "v2ray.json";
           text = builtins.toJSON cfg.config;
           checkPhase = ''
  -          ${pkgs.v2ray}/bin/v2ray -test -config $out
  +          ${cfg.package}/bin/v2ray -test -config $out
           '';
         };
   
  
positive.code:       description = "v2ray Daemon";
        after = [ "network.target" ];
        wantedBy = [ "multi-user.target" ];
        path = [ pkgs.v2ray ];
        script = ''
          exec v2ray -config ${configFile}
        '';
      };
    };
  }
  
negative.code:           Whether to run v2ray server.
  
            Either <literal>configFile</literal> or <literal>config</literal> must be specified.
          '';
        };
  
        package = mkOption {
          type = types.package;
          default = pkgs.v2ray;
          defaultText = literalExpression "pkgs.v2ray";
          description = ''
            Which v2ray package to use.
          '';
        };
  
  