examples: update Go example (#7217)

Update the Go example to use Go modules: Move the example into a
directory containing a go.mod file, change the installation instructions
to use "go install".

Update the go_package option in addressbook.proto to an actual module path.

Update examples to use the google.golang.org/protobuf/proto module.

examples/Makefile

@@ -16,7 +16,7 @@ clean:
 	rm -f javac_middleman AddPerson*.class ListPeople*.class com/example/tutorial/*.class
 	rm -f protoc_middleman addressbook.pb.cc addressbook.pb.h addressbook_pb2.py com/example/tutorial/AddressBookProtos.java
 	rm -f *.pyc
-	rm -f protoc_middleman_go tutorial/*.pb.go add_person_go list_people_go go.mod go.sum
+	rm -f go/tutorialpb/*.pb.go add_person_go list_people_go
 	rm -f protoc_middleman_dart dart_tutorial/*.pb*.dart
 	rmdir dart_tutorial 2>/dev/null || true
 	rmdir tutorial 2>/dev/null || true
@@ -28,10 +28,9 @@ protoc_middleman: addressbook.proto
 	protoc $$PROTO_PATH --cpp_out=. --java_out=. --python_out=. addressbook.proto
 	@touch protoc_middleman
 
-protoc_middleman_go: addressbook.proto
-	mkdir -p tutorial # make directory for go package
-	protoc $$PROTO_PATH --go_out=tutorial addressbook.proto
-	@touch protoc_middleman_go
+go/tutorialpb/addressbook.pb.go: addressbook.proto
+	mkdir -p go/tutorialpb # make directory for go package
+	protoc $$PROTO_PATH --go_opt=paths=source_relative --go_out=go/tutorialpb addressbook.proto
 
 protoc_middleman_dart: addressbook.proto
 	mkdir -p dart_tutorial # make directory for the dart package
@@ -51,21 +50,17 @@ add_person_dart: add_person.dart protoc_middleman_dart
 
 list_people_dart: list_people.dart protoc_middleman_dart
 
-go_mod:
-	go mod init github.com/protocolbuffers/protobuf/examples
-	go mod tidy
+add_person_go: go/cmd/add_person/add_person.go go/tutorialpb/addressbook.pb.go
+	cd go && go build -o ../add_person_go ./cmd/add_person
 
-add_person_go: add_person.go protoc_middleman_go go_mod
-	go build -o add_person_go add_person.go
+add_person_gotest: go/tutorialpb/addressbook.pb.go
+	cd go && go test ./cmd/add_person
 
-add_person_gotest: add_person_test.go add_person_go go_mod
-	go test add_person.go add_person_test.go
+list_people_go: go/cmd/list_people/list_people.go go/tutorialpb/addressbook.pb.go
+	cd go && go build -o ../list_people_go ./cmd/list_people
 
-list_people_go: list_people.go protoc_middleman_go go_mod
-	go build -o list_people_go list_people.go
-
-list_people_gotest: list_people.go list_people_go go_mod
-	go test list_people.go list_people_test.go
+list_people_gotest: go/tutorialpb/addressbook.pb.go
+	cd go && go test ./cmd/list_people
 
 javac_middleman: AddPerson.java ListPeople.java protoc_middleman
 	javac -cp $$CLASSPATH AddPerson.java ListPeople.java com/example/tutorial/AddressBookProtos.java

examples/README.md

@@ -91,22 +91,18 @@ scripts) and can be used to create/display an address book data file.
 
 ### Go
 
-The Go example requires a plugin to the protocol buffer compiler, so it is not
-build with all the other examples.  See:
+Follow instructions in [../README.md](../README.md) to install protoc. Then
+install the Go protoc plugin (protoc-gen-go):
 
-    https://github.com/golang/protobuf
+    $ go install google.golang.org/protobuf/cmd/protoc-gen-go@latest
 
-for more information about Go protocol buffer support.
+The "go install" command will install protoc-gen-go into the GOBIN
+directory.  You can set the $GOBIN environment variable before
+running "go install" to change the install location.  Make sure the
+install directory is in your shell $PATH.
 
-First, install the Protocol Buffers compiler (protoc).
-
-Then, install the Go Protocol Buffers plugin ($GOPATH/bin must be in your $PATH
-for protoc to find it):
-
-    go get github.com/golang/protobuf/protoc-gen-go
-
-Build the Go samples in this directory with "make go".  This creates the
-following executable files in the current directory:
+Build the Go samples with "make go".  This creates the following
+executable files in the current directory:
 
     add_person_go      list_people_go
 

examples/addressbook.proto

@@ -24,7 +24,7 @@ option csharp_namespace = "Google.Protobuf.Examples.AddressBook";
 // [END csharp_declaration]
 
 // [START go_declaration]
-option go_package = "../tutorial";
+option go_package = "github.com/protocolbuffers/protobuf/examples/go/tutorialpb";
 // [END go_declaration]
 
 // [START messages]

examples/go/cmd/add_person/add_person.go

@@ -9,8 +9,8 @@ import (
 	"os"
 	"strings"
 
-	"github.com/golang/protobuf/proto"
-	pb "github.com/protocolbuffers/protobuf/examples/tutorial"
+	pb "github.com/protocolbuffers/protobuf/examples/go/tutorialpb"
+	"google.golang.org/protobuf/proto"
 )
 
 func promptForAddress(r io.Reader) (*pb.Person, error) {

examples/go/cmd/add_person/add_person_test.go

@@ -4,8 +4,8 @@ import (
 	"strings"
 	"testing"
 
-	"github.com/golang/protobuf/proto"
-	pb "github.com/protocolbuffers/protobuf/examples/tutorial"
+	pb "github.com/protocolbuffers/protobuf/examples/go/tutorialpb"
+	"google.golang.org/protobuf/proto"
 )
 
 func TestPromptForAddressReturnsAddress(t *testing.T) {
@@ -51,7 +51,7 @@ unknown
 	}
 	for i := 0; i < phones; i++ {
 		if !proto.Equal(got.Phones[i], want[i]) {
-			t.Errorf("want phone %q, got %q", *want[i], *got.Phones[i])
+			t.Errorf("want phone %q, got %q", want[i], got.Phones[i])
 		}
 
 	}

examples/go/cmd/list_people/list_people.go

@@ -7,8 +7,8 @@ import (
 	"log"
 	"os"
 
-	"github.com/golang/protobuf/proto"
-	pb "github.com/protocolbuffers/protobuf/examples/tutorial"
+	pb "github.com/protocolbuffers/protobuf/examples/go/tutorialpb"
+	"google.golang.org/protobuf/proto"
 )
 
 func writePerson(w io.Writer, p *pb.Person) {

examples/go/cmd/list_people/list_people_test.go

@@ -5,7 +5,7 @@ import (
 	"strings"
 	"testing"
 
-	pb "github.com/protocolbuffers/protobuf/examples/tutorial"
+	pb "github.com/protocolbuffers/protobuf/examples/go/tutorialpb"
 )
 
 func TestWritePersonWritesPerson(t *testing.T) {

examples/go/go.mod

@@ -0,0 +1,5 @@
+module github.com/protocolbuffers/protobuf/examples/go
+
+go 1.14
+
+require google.golang.org/protobuf v1.27.1

examples/go/go.sum

@@ -0,0 +1,6 @@
+github.com/golang/protobuf v1.5.0/go.mod h1:FsONVRAS9T7sI+LIUmWTfcYkHO4aIWwzhcaSAoJOfIk=
+github.com/google/go-cmp v0.5.5/go.mod h1:v8dTdLbMG2kIc/vJvl+f65V22dbkXbowE6jgT/gNBxE=
+golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
+google.golang.org/protobuf v1.26.0-rc.1/go.mod h1:jlhhOSvTdKEhbULTjvd4ARK9grFBp09yW+WbY/TyQbw=
+google.golang.org/protobuf v1.27.1 h1:SnqbnDw1V7RiZcXPx5MEeqPv2s79L9i7BJUlG/+RurQ=
+google.golang.org/protobuf v1.27.1/go.mod h1:9q0QmTI4eRPtz6boOQmLYwt+qCgq0jsYwAQnmE0givc=