To run the example you need to obtain the built rust library.
# On M1+ Mac (note arch)
curl -fsSL https://github.com/daulet/tokenizers/releases/download/v1.20.2/libtokenizers.darwin-aarch64.tar.gz | tar xvz
# change -L argument to where you've placed the library download above
go run -ldflags="-extldflags '-L$(pwd)'" main.go
or make build from the parent directory and go run -ldflags="-extldflags '-L..'" main.go