I know its late already, but it worked for me and i hope it helps.
1 – delete dockerfile present in the project
2 – then right click on the project > add > Docker support
3 – choose between widows or linux
This will recreate the dockerfile and add Microsoft.VisualStudio.Azure.Containers.Tools.Targets to your nugget dependencies. Updates will maybe be required.
4 – Run and should be just fine