fix linter errors

src/cmd/tools/dtest/docker/harness/resources/coordinator.go

@@ -22,7 +22,7 @@ package resources
 
 import (
 	"bytes"
-	"encoding/json"
+	"context"
 	"fmt"
 	"io/ioutil"
 	"net"
@@ -32,6 +32,7 @@ import (
 	"github.com/m3db/m3/src/query/generated/proto/admin"
 
 	"github.com/gogo/protobuf/jsonpb"
+	"github.com/gogo/protobuf/proto"
 	"github.com/ory/dockertest"
 	"go.uber.org/zap"
 )
@@ -240,13 +241,7 @@ func (c *coordinator) CreateDatabase(
 		zapMethod("createDatabase"), zap.String("url", url),
 		zap.String("request", addRequest.String()))
 
-	b, err := json.Marshal(addRequest)
-	if err != nil {
-		logger.Error("failed to marshal", zap.Error(err))
-		return admin.DatabaseCreateResponse{}, err
-	}
-
-	resp, err := http.Post(url, "application/json", bytes.NewReader(b))
+	resp, err := makePostRequest(logger, url, &addRequest)
 	if err != nil {
 		logger.Error("failed post", zap.Error(err))
 		return admin.DatabaseCreateResponse{}, err
@@ -274,15 +269,7 @@ func (c *coordinator) AddNamespace(
 		zapMethod("addNamespace"), zap.String("url", url),
 		zap.String("request", addRequest.String()))
 
-	marshaller := jsonpb.Marshaler{EmitDefaults: true}
-	data := bytes.NewBuffer(nil)
-	err := marshaller.Marshal(data, &addRequest)
-	if err != nil {
-		logger.Error("failed to marshal", zap.Error(err))
-		return admin.NamespaceGetResponse{}, err
-	}
-
-	resp, err := http.Post(url, "application/json", data)
+	resp, err := makePostRequest(logger, url, &addRequest)
 	if err != nil {
 		logger.Error("failed post", zap.Error(err))
 		return admin.NamespaceGetResponse{}, err
@@ -333,6 +320,26 @@ func (c *coordinator) WriteCarbon(
 	// return nil
 }
 
+func makePostRequest(logger *zap.Logger, url string, body proto.Message) (*http.Response, error) {
+	data := bytes.NewBuffer(nil)
+	if err := (&jsonpb.Marshaler{}).Marshal(data, body); err != nil {
+		logger.Error("failed to marshal", zap.Error(err))
+
+		return &http.Response{}, fmt.Errorf("failed to marshal: %w", err)
+	}
+
+	req, err := http.NewRequestWithContext(context.Background(), http.MethodPost, url, data)
+	if err != nil {
+		logger.Error("failed to construct request", zap.Error(err))
+
+		return &http.Response{}, fmt.Errorf("failed to construct request: %w", err)
+	}
+
+	req.Header.Add("Content-Type", "application/json")
+
+	return http.DefaultClient.Do(req)
+}
+
 func (c *coordinator) query(
 	verifier GoalStateVerifier, query string,
 ) error {