Codestyle: Fix some goconst issues (#17530)

Signed-off-by: Mario Trangoni <mjtrangoni@gmail.com>

pkg/api/http_server.go

@@ -258,7 +258,7 @@ func (hs *HTTPServer) metricsEndpoint(ctx *macaron.Context) {
 		return
 	}
 
-	if ctx.Req.Method != "GET" || ctx.Req.URL.Path != "/metrics" {
+	if ctx.Req.Method != http.MethodGet || ctx.Req.URL.Path != "/metrics" {
 		return
 	}
 

pkg/api/playlist.go

 package api
 
 import (
+	"net/http"
+
 	"github.com/grafana/grafana/pkg/bus"
 	_ "github.com/grafana/grafana/pkg/infra/log"
 	m "github.com/grafana/grafana/pkg/models"
@@ -33,7 +35,7 @@ func ValidateOrgPlaylist(c *m.ReqContext) {
 		return
 	}
 
-	if len(items) == 0 && c.Context.Req.Method != "DELETE" {
+	if len(items) == 0 && c.Context.Req.Method != http.MethodDelete {
 		c.JsonApiErr(404, "Playlist is empty", itemsErr)
 		return
 	}

pkg/setting/setting_test.go

 package setting
 
 import (
-	"gopkg.in/ini.v1"
 	"os"
 	"path"
 	"path/filepath"
 	"runtime"
 	"testing"
 
+	"gopkg.in/ini.v1"
+
 	. "github.com/smartystreets/goconvey/convey"
 )
 
+const (
+	windows = "windows"
+)
+
 func TestLoadingSettings(t *testing.T) {
 
 	Convey("Testing loading settings from ini file", t, func() {
@@ -72,7 +77,7 @@ func TestLoadingSettings(t *testing.T) {
 		})
 
 		Convey("Should be able to override via command line", func() {
-			if runtime.GOOS == "windows" {
+			if runtime.GOOS == windows {
 				cfg := NewCfg()
 				cfg.Load(&CommandLineArgs{
 					HomePath: "../../",
@@ -106,7 +111,7 @@ func TestLoadingSettings(t *testing.T) {
 		})
 
 		Convey("Defaults can be overridden in specified config file", func() {
-			if runtime.GOOS == "windows" {
+			if runtime.GOOS == windows {
 				cfg := NewCfg()
 				cfg.Load(&CommandLineArgs{
 					HomePath: "../../",
@@ -128,7 +133,7 @@ func TestLoadingSettings(t *testing.T) {
 		})
 
 		Convey("Command line overrides specified config file", func() {
-			if runtime.GOOS == "windows" {
+			if runtime.GOOS == windows {
 				cfg := NewCfg()
 				cfg.Load(&CommandLineArgs{
 					HomePath: "../../",
@@ -150,7 +155,7 @@ func TestLoadingSettings(t *testing.T) {
 		})
 
 		Convey("Can use environment variables in config values", func() {
-			if runtime.GOOS == "windows" {
+			if runtime.GOOS == windows {
 				os.Setenv("GF_DATA_PATH", `c:\tmp\env_override`)
 				cfg := NewCfg()
 				cfg.Load(&CommandLineArgs{