(This official repo's protobuf-compiler is out-dated.)
(Unrecognized syntax identifier "proto3". This parser only recognizes "proto2".)
$ wget https://github.com/protocolbuffers/protobuf/releases/download/v3.11.4/protoc-3.11.4-linux-x86_64.zip
$ unzip protoc-3.11.4-linux-x86_64.zip
$ sudo cp -rv bin include /usr/local
$ git clone https://github.com/andelf/rust-tron.git
$ cd rust-tron
$ cargo build --all