ASP.NET Core and Heroku - Dockerfile - https://codingblast.com/hosting-asp-net-core-on-heroku-with-dockercircleci-for-free/

Dockerfile

FROM microsoft/dotnet:2.2-sdk AS build-env
WORKDIR /app

# Copy csproj and restore as distinct layers
COPY *.csproj ./
RUN dotnet restore

# Copy everything else and build
COPY . ./
RUN dotnet publish -c Release -o out

# Build runtime image
FROM microsoft/dotnet:2.2-aspnetcore-runtime
ENV PORT=5000
WORKDIR /app
COPY --from=build-env /app/out .
CMD ASPNETCORE_URLS=http://*:$PORT dotnet AspNetCoreHerokuDocker.dll