FYI for Mac Users - El Capitan

[C.H.A.D.o]

If you have problem with mono on beta 3
Error: “could not discover the mach TLS offset”

To solve this, I compile mono from master branch

git clone GitHub - mono/mono: Mono open source ECMA CLI, C# and .NET implementation.
cd mono
PREFIX=/usr/local
PATH=$PREFIX/bin:$PATH
./autogen.sh --prefix=$PREFIX --disable-nls
make get-monolite-latest
make
sudo make install

Also remove old mono installation, if you have

And use Unreal Engine from promoted or master branch too