NuGet Error NU5042

project.json pack is disabled in the current NuGet version, and will be permanently removed in a future version. Please consider migrating 'MyProject' to PackageReference and using the pack targets. You can set the 'NUGET_ENABLE_LEGACY_PROJECT_JSON_PACK' environment variable to 'true' to temporarily reenable this functionality.

Issue

NuGet.exe pack for project.json projects is not supported.

Solution

Migrate your project to PackageReference and use the pack targets instead.