Install .NET Core on macOS 10.11+, after install homebrew:
brew update
brew install openssl
mkdir -p /usr/local/lib
ln -s /usr/local/opt/openssl/lib/libcrypto.1.0.0.dylib /usr/local/lib/
ln -s /usr/local/opt/openssl/lib/libssl.1.0.0.dylib /usr/local/lib/
Install .NET Core SDK from https://go.microsoft.com/fwlink/?LinkID=835011
Official Microsoft .NET Core page with installation guides for Windows, Linux, Mac and Docker
Detailed instructions on getting .net-core set up or installed.