MessagePack is an efficient binary serialization format. It lets you exchange data among multiple languages like JSON. But it's faster and smaller. Small integers are encoded into a single byte, and typical short strings require only one extra byte in addition to the strings themselves. https://msgpack.org
The Context.MsgPack(v) is the method which sends MessagePack responses to the client. It accepts any Go value. As always, if it's a struct value, the fields should be exported.