A very short example of how to use Protocol Buffers in Go. This is proto3, i.e. the 3rd version of the protocol, but the example is generally valid for the second version as well. Preparation Go to this to read, download, and install (everything is simple there). link Installation instructions in Go can be found : here go get -u github.com/golang/protobuf/{proto,protoc-gen-go} You may need to use if you have something like this in : -f ~/.gitconfig [url "ssh://git@github.com/"] insteadOf = https://github.com/ Example For this example, we will save an array of numbers and a string, and then read them back. Furthermore, we will assume that we are in the root of our new project. The proto-file will look like this: msg/msg.proto // comments follow a style C/C++ /* and multiline too */ syntax = "proto3"; // package name, this will be saved in the resulting go-file package msg; // type of data to be saved message msg { // type field_name = field_number string key = 1; // repeated means slice repeated int64 value = 2; } /* In the third version, there are no required fields and extensions. Instead of extensions, the type `Any` is implemented (more on that later) */ Now, we need to compile the proto file: protoc --go_out=. msg/*.proto The result will be a file like this: msg/msg.pb.go package msg import proto "github.com/golang/protobuf/proto" var _ = proto.Marshal /* The structure looks like this. Note that tags for JSON have been added automatically */ type Msg struct { Key string `protobuf: "bytes,1,opt,name=key" json: "key,omitempty"` Value []int64 `protobuf: "varint,2,rep,name=value" json: "value,omitempty"` } // methods are needed to make the structure conform to the proto.Message interface func (m *Msg) Reset() { *m = Msg{} } func (m *Msg) String() string { return proto.CompactTextString(m) } func (*Msg) ProtoMessage() {} func init() { } Now let's create a structure, write its bytes, and read it back: main.go package main import ( "log" "./msg" "github.com/golang/protobuf/proto" ) func main() { // create a new "message" msg1 := &msg.Msg{ Key: "Hello Protocol Buffers", Value: []int64{1, 2, 3, 4}, } // structure to bytes data, err := proto.Marshal(msg1) if err != nil { log.Fatal("marshaling error: ", err) return } // how much memory does it take? log.Printf("data length: %d", len(data)) // bytes into the structure msg2 := new(msg.msg) err = proto.Unmarshal(data, msg2) if err != nil { log.Fatal("unmarshaling error: ", err) } // now both structures must be equal if msg1.Key != msg2.Key { log.Printf("unexpected value, expected '%s', got '%s'", msg1.Key, msg2.Key) } for i := 0; i < 4; i++ { if msg1.Value[i] != msg2.Value[i] { log.Printf("unexpected value, expected %d, got %d", msg1.Value[i], msg2.Value[i]) } } log.Println("Done") } As you can see, it's easy. If we dig deeper, let's say there is a desire to create a database that stores "messages" - so that the type of "message" is not initially defined, and to store these "messages" in some structure. In other words, to have a library that will store what we give it in a certain format. In proto3 type is implemented to store any type. Any Type looks like this: Any message Any { string type_url = 1; // type bytes value = 2; // type content in bytes } Links Protocol Buffers GitHub Releases Protocol Buffers Issue Tracker One of the Protocol Buffers implementations for Go Guide to Protocol Buffers v3
