Replace deprecated github.com/golang/protobuf package

This replaces usage of proto.{Float64,Int32,Int64,String,Uint32,Uint64},
which doesn't break the interface.

And replaces ptypes.TimestampProto by google.golang.org/protobuf/types/known/timestamppb.
This works since github.com/golang/protobuf has been bumped to v1.5.2,
which makes ptypes.TimestampProto an alias to timestamppb.Timestamp.
This is only used test (openmetrics_create_test.go), which won't break
interfaces.

Updates: prometheus#317

Signed-off-by: Shengjing Zhu <zhsj@debian.org>

expfmt/decode_test.go

@@ -22,10 +22,10 @@ import (
 	"strings"
 	"testing"
 
-	"github.com/golang/protobuf/proto" //nolint:staticcheck // Ignore SA1019. Need to keep deprecated package for compatibility.
-	dto "github.com/prometheus/client_model/go"
-
 	"github.com/prometheus/common/model"
+
+	dto "github.com/prometheus/client_model/go"
+	"google.golang.org/protobuf/proto"
 )
 
 func TestTextDecoder(t *testing.T) {
@@ -100,8 +100,7 @@ mf2 4
 }
 
 func TestProtoDecoder(t *testing.T) {
-
-	var testTime = model.Now()
+	testTime := model.Now()
 
 	scenarios := []struct {
 		in       string
@@ -369,7 +368,7 @@ func TestProtoDecoder(t *testing.T) {
 }
 
 func testDiscriminatorHTTPHeader(t testing.TB) {
-	var scenarios = []struct {
+	scenarios := []struct {
 		input  map[string]string
 		output Format
 	}{
@@ -435,7 +434,7 @@ func TestExtractSamples(t *testing.T) {
 			Help: proto.String("Help for foo."),
 			Type: dto.MetricType_COUNTER.Enum(),
 			Metric: []*dto.Metric{
-				&dto.Metric{
+				{
 					Counter: &dto.Counter{
 						Value: proto.Float64(4711),
 					},
@@ -447,7 +446,7 @@ func TestExtractSamples(t *testing.T) {
 			Help: proto.String("Help for bar."),
 			Type: dto.MetricType_GAUGE.Enum(),
 			Metric: []*dto.Metric{
-				&dto.Metric{
+				{
 					Gauge: &dto.Gauge{
 						Value: proto.Float64(3.14),
 					},
@@ -459,7 +458,7 @@ func TestExtractSamples(t *testing.T) {
 			Help: proto.String("Help for bad."),
 			Type: dto.MetricType(42).Enum(),
 			Metric: []*dto.Metric{
-				&dto.Metric{
+				{
 					Gauge: &dto.Gauge{
 						Value: proto.Float64(2.7),
 					},

expfmt/encode_test.go

@@ -18,8 +18,8 @@ import (
 	"net/http"
 	"testing"
 
-	"github.com/golang/protobuf/proto" //nolint:staticcheck // Ignore SA1019. Need to keep deprecated package for compatibility.
 	dto "github.com/prometheus/client_model/go"
+	"google.golang.org/protobuf/proto"
 )
 
 func TestNegotiate(t *testing.T) {