chore: enable more linter (#1557)

pkg/config/config.go

@@ -42,39 +42,24 @@ func NewResolver(file string, logger log.Logger, insecureSkipVerify bool) (*Reso
 	var fileBytes []byte
 	var err error
 	if strings.HasPrefix(file, "http://") || strings.HasPrefix(file, "https://") {
-		_ = level.Info(logger).Log("msg", fmt.Sprintf("Loading configuration file from URL: %v", file))
-		tr := &http.Transport{
-			TLSClientConfig: &tls.Config{InsecureSkipVerify: insecureSkipVerify}, //nolint:gosec
-		}
-		if insecureSkipVerify {
-			_ = level.Warn(logger).Log("msg", "Loading configuration file with TLS verification disabled")
-		}
-		client := &http.Client{Transport: tr}
-		resp, err := client.Get(file)
-		if err != nil {
-			return nil, err
-		}
-		defer resp.Body.Close()
-		fileBytes, err = io.ReadAll(resp.Body)
+		fileBytes, err = readFromURL(file, logger, insecureSkipVerify)
 		if err != nil {
 			return nil, err
 		}
 	} else {
-		_ = level.Info(logger).Log("msg", fmt.Sprintf("Loading configuration file: %v", file))
-		if _, err := os.Stat(file); err != nil {
-			return nil, err
-		}
-		fileBytes, err = os.ReadFile(file)
+		fileBytes, err = readFromFile(file, logger)
 		if err != nil {
 			return nil, err
 		}
 	}
 
 	var rawValues map[string]interface{}
+
 	err = yaml.Unmarshal(fileBytes, &rawValues)
 	if err != nil {
 		return nil, err
 	}
+
 	// Flatten nested YAML values
 	flattenedValues := flatten(rawValues)
 	for k, v := range flattenedValues {
@@ -82,9 +67,51 @@ func NewResolver(file string, logger log.Logger, insecureSkipVerify bool) (*Reso
 			flags[k] = v
 		}
 	}
+
 	return &Resolver{flags: flags}, nil
 }
 
+func readFromFile(file string, logger log.Logger) ([]byte, error) {
+	_ = level.Info(logger).Log("msg", fmt.Sprintf("Loading configuration file: %v", file))
+	if _, err := os.Stat(file); err != nil {
+		return nil, err
+	}
+
+	fileBytes, err := os.ReadFile(file)
+	if err != nil {
+		return nil, err
+	}
+
+	return fileBytes, err
+}
+
+func readFromURL(file string, logger log.Logger, insecureSkipVerify bool) ([]byte, error) {
+	_ = level.Info(logger).Log("msg", fmt.Sprintf("Loading configuration file from URL: %v", file))
+	tr := &http.Transport{
+		TLSClientConfig: &tls.Config{InsecureSkipVerify: insecureSkipVerify}, //nolint:gosec
+	}
+
+	if insecureSkipVerify {
+		_ = level.Warn(logger).Log("msg", "Loading configuration file with TLS verification disabled")
+	}
+
+	client := &http.Client{Transport: tr}
+
+	resp, err := client.Get(file)
+	if err != nil {
+		return nil, err
+	}
+
+	defer resp.Body.Close()
+
+	fileBytes, err := io.ReadAll(resp.Body)
+	if err != nil {
+		return nil, err
+	}
+
+	return fileBytes, nil
+}
+
 func (c *Resolver) setDefault(v getFlagger) {
 	for name, value := range c.flags {
 		f := v.GetFlag(name)

pkg/config/flatten.go

@@ -9,7 +9,7 @@ import (
 //
 // All keys will be joined by dot
 // e.g. {"a": {"b":"c"}} => {"a.b":"c"}
-// or {"a": {"b":[1,2]}} => {"a.b.0":1, "a.b.1": 2}
+// or {"a": {"b":[1,2]}} => {"a.b.0":1, "a.b.1": 2}.
 func flatten(data map[string]interface{}) map[string]string {
 	ret := make(map[string]string)
 	for k, v := range data {
@@ -32,6 +32,7 @@ func flatten(data map[string]interface{}) map[string]string {
 	}
 	return ret
 }
+
 func flattenSlice(data []interface{}) map[string]string {
 	ret := make(map[string]string)
 	for idx, v := range data {

pkg/config/flatten_test.go

@@ -7,8 +7,10 @@ import (
 	"gopkg.in/yaml.v3"
 )
 
-// Unmarshal good configuration file and confirm data is flattened correctly
+// Unmarshal good configuration file and confirm data is flattened correctly.
 func TestConfigFlattening(t *testing.T) {
+	t.Parallel()
+
 	goodYamlConfig := []byte(`---
 
     collectors: