Enable revive linter (prometheus-community#519)

* Bump Go to 1.17
* Bump prometheus orb to 0.15.0
* Enable `revive` linter.
* Fixup linter nits.

Signed-off-by: SuperQ <superq@gmail.com>

.circleci/config.yml

@@ -2,13 +2,13 @@
 version: 2.1
 
 orbs:
-  prometheus: prometheus/prometheus@0.11.0
+  prometheus: prometheus/prometheus@0.15.0
 
 executors:
   # This must match .promu.yml.
   golang:
     docker:
-      - image: circleci/golang:1.16
+      - image: circleci/golang:1.17
 
 jobs:
   test:

.golangci.yml

@@ -1,4 +1,8 @@
 ---
+linters:
+  enable:
+    - revive
+
 issues:
   exclude-rules:
     - path: _test.go

.promu.yml

@@ -1,6 +1,6 @@
 go:
     # This must match .circle/config.yml.
-    version: 1.16
+    version: 1.17
 repository:
     path: github.com/prometheus-community/elasticsearch_exporter
 build:

collector/indices_settings_test.go

@@ -80,7 +80,7 @@ func TestIndicesSettings(t *testing.T) {
 			// 	t.Errorf("Wrong setting for cluster routing allocation enabled")
 			// }
 			var counter int
-			var total_fields int
+			var totalFields int
 			for key, value := range nsr {
 				if value.Settings.IndexInfo.Blocks.ReadOnly == "true" {
 					counter++
@@ -89,7 +89,7 @@ func TestIndicesSettings(t *testing.T) {
 					}
 				}
 				if value.Settings.IndexInfo.Mapping.TotalFields.Limit == "10000" {
-					total_fields++
+					totalFields++
 					if key != "instagram" {
 						t.Errorf("Expected 10000 total_fields only for  instagram")
 					}
@@ -98,7 +98,7 @@ func TestIndicesSettings(t *testing.T) {
 			if counter != 2 {
 				t.Errorf("Wrong number of read_only indexes")
 			}
-			if total_fields != 1 {
+			if totalFields != 1 {
 				t.Errorf(("Wrong number of total_fields found"))
 			}
 		}