"metadata": [
    {
      "src": "*.csproj",
      "dest": "temp/api/netstandard2.0",
      "properties": {
          "TargetFramework": "netstandard2.0"
      }
    },
      {
        "src": "*.csproj",
        "dest": "temp/api/net40",
        "properties": {
            "TargetFramework": "net40"
        }
    },
      {
        "src": "*.csproj",
        "dest": "temp/api/net46",
        "properties": {
            "TargetFramework": "net46"
        }
    }
  ],
  "merge": {
    "content": [
        {
            "files": "*.yml",
            "src": "temp/api/net40"
        },
        {
            "files": "*.yml",
            "src": "temp/api/net46"
        },
        {
          "files": "*.yml",
          "src": "temp/api/netstandard2.0"
        }
    ],
    "fileMetadata": {
        "platform": {
            "temp/api/net40/*.yml": [
                "net40"
            ],
            "temp/api/net46/*.yml": [
                "net46"
            ],
            "temp/api/netstandard2.0/*.yml": [
              "netstandard2.0"
          ]
        }
    },
    "dest": "api"
}

[18-07-12 03:10:53.343]Info:[MetadataCommand]Completed Scope:MetadataCommand in 17778.9324 milliseconds.
[18-07-12 03:10:53.387]Info:[MergeCommand.Merge Metadata]Start merge metadata...
[18-07-12 03:10:55.891]Error:[MergeCommand]System.NullReferenceException: Object reference not set to an instance of an object.
   at Microsoft.DocAsCode.Build.Engine.HostServiceCreator.LoadModels(IEnumerable`1 files, DocumentBuildParameters parameters, IDocumentProcessor processor)
   at Microsoft.DocAsCode.Build.Engine.HostServiceCreator.CreateHostService(DocumentBuildParameters parameters, TemplateProcessor templateProcessor, IMarkdownService markdownService, IEnumerable`1 metadataValidator, IDocumentProcessor processor, IEnumerable`1 files)
   at Microsoft.DocAsCode.Build.Engine.SingleDocumentBuilder.Build(IDocumentProcessor processor, DocumentBuildParameters parameters, IMarkdownService markdownService)
   at Microsoft.DocAsCode.SubCommands.MetadataMerger.MergePageViewModel(MetadataMergeParameters parameters)
   at Microsoft.DocAsCode.SubCommands.MetadataMerger.Merge(MetadataMergeParameters parameters)
   at Microsoft.DocAsCode.SubCommands.MergeCommand.MergeDocument(String baseDirectory, String outputDirectory)
[18-07-12 03:10:55.912]Info:[MergeCommand]Completed Scope:MergeCommand in 2568.157 milliseconds.