refactor: apply code style and linter improvements across Go files

- Refactor file locking parameters into top-level constants in filelock.go for improved maintainability.
- Replace duplicated error handling durations and retry settings with reusable constants in file locking logic.
- Update for-loops to use range-based iteration on integer variables for better Go style in tests and concurrency code.
- Replace usage of fmt.Errorf with errors.New for static error strings.
- Prefer named http.Method* constants over string literals for HTTP methods in main.go and tests.
- Use map[string]any instead of map[string]interface{} for type declarations.
- Add and fine-tune multiple linters and their configurations in .golangci.yml; introduce new linter settings and rules, improve output formatting, and remove several linters no longer used.
- Update comments or linter ignore statements for greater clarity.
- Use a min() helper rather than manual interval capping in polling logic.

Signed-off-by: appleboy <appleboy.tw@gmail.com>

Author: appleboy

.golangci.yml

@@ -1,49 +1,118 @@
 version: "2"
+output:
+  sort-order:
+    - file
 linters:
   default: none
   enable:
+    - bidichk
     - bodyclose
-    - dogsled
-    - dupl
+    - depguard
     - errcheck
-    - exhaustive
-    - goconst
+    - forbidigo
+    - gocheckcompilerdirectives
     - gocritic
-    - gocyclo
-    - goprintffuncname
-    - gosec
     - govet
     - ineffassign
-    - misspell
+    - mirror
+    - modernize
     - nakedret
-    - noctx
+    - nilnil
     - nolintlint
-    - rowserrcheck
+    - perfsprint
+    - revive
     - staticcheck
+    - testifylint
     - unconvert
     - unparam
     - unused
-    - whitespace
+    - usestdlibvars
+    - usetesting
+    - wastedassign
+  settings:
+    depguard:
+      rules:
+        main:
+          deny:
+            - pkg: io/ioutil
+              desc: use os or io instead
+            - pkg: golang.org/x/exp
+              desc: it's experimental and unreliable
+            - pkg: github.com/pkg/errors
+              desc: use builtin errors package instead
+    nolintlint:
+      allow-unused: false
+      require-explanation: true
+      require-specific: true
+    gocritic:
+      enabled-checks:
+        - equalFold
+      disabled-checks: []
+    revive:
+      severity: error
+      rules:
+        - name: blank-imports
+        - name: constant-logical-expr
+        - name: context-as-argument
+        - name: context-keys-type
+        - name: dot-imports
+        - name: empty-lines
+        - name: error-return
+        - name: error-strings
+        - name: exported
+        - name: identical-branches
+        - name: if-return
+        - name: increment-decrement
+        - name: modifies-value-receiver
+        - name: package-comments
+        - name: redefines-builtin-id
+        - name: superfluous-else
+        - name: time-naming
+        - name: unexported-return
+        - name: var-declaration
+        - name: var-naming
+          disabled: true
+    staticcheck:
+      checks:
+        - all
+    testifylint: {}
+    usetesting:
+      os-temp-dir: true
+    forbidigo:
+      forbid:
+        - pattern: "^(print|println)$"
+          msg: "use fmt.Print* instead of built-in print/println"
+    perfsprint:
+      concat-loop: false
+    govet:
+      enable:
+        - nilness
+        - unusedwrite
   exclusions:
     generated: lax
     presets:
       - comments
       - common-false-positives
       - legacy
       - std-error-handling
-    paths:
-      - third_party$
-      - builtin$
-      - examples$
+    rules:
+      - linters:
+          - errcheck
+          - staticcheck
+          - unparam
+        path: _test\.go
+issues:
+  max-issues-per-linter: 0
+  max-same-issues: 0
 formatters:
   enable:
     - gofmt
     - gofumpt
-    - goimports
     - golines
+  settings:
+    gofumpt:
+      extra-rules: true
   exclusions:
     generated: lax
-    paths:
-      - third_party$
-      - builtin$
-      - examples$
+run:
+  timeout: 10m

filelock.go

@@ -6,6 +6,12 @@ import (
 	"time"
 )
 
+const (
+	lockMaxRetries   = 50
+	lockRetryDelay   = 100 * time.Millisecond
+	staleLockTimeout = 30 * time.Second
+)
+
 // fileLock represents a file lock.
 type fileLock struct {
 	lockFile *os.File
@@ -16,10 +22,8 @@ type fileLock struct {
 // Uses a separate lock file to coordinate access across processes.
 func acquireFileLock(filePath string) (*fileLock, error) {
 	lockPath := filePath + ".lock"
-	maxRetries := 50
-	retryDelay := 100 * time.Millisecond
 
-	for i := 0; i < maxRetries; i++ {
+	for range lockMaxRetries {
 		lockFile, err := os.OpenFile(lockPath, os.O_CREATE|os.O_EXCL|os.O_WRONLY, 0o600)
 		if err == nil {
 			fmt.Fprintf(lockFile, "%d", os.Getpid())
@@ -31,7 +35,7 @@ func acquireFileLock(filePath string) (*fileLock, error) {
 
 		if os.IsExist(err) {
 			if info, statErr := os.Stat(lockPath); statErr == nil {
-				if time.Since(info.ModTime()) > 30*time.Second {
+				if time.Since(info.ModTime()) > staleLockTimeout {
 					if remErr := os.Remove(lockPath); remErr != nil && !os.IsNotExist(remErr) {
 						return nil, fmt.Errorf(
 							"failed to remove stale lock file %s: %w",
@@ -42,7 +46,7 @@ func acquireFileLock(filePath string) (*fileLock, error) {
 					continue
 				}
 			}
-			time.Sleep(retryDelay)
+			time.Sleep(lockRetryDelay)
 			continue
 		}
 
@@ -51,7 +55,7 @@ func acquireFileLock(filePath string) (*fileLock, error) {
 
 	return nil, fmt.Errorf(
 		"timeout waiting for file lock after %v",
-		time.Duration(maxRetries)*retryDelay,
+		time.Duration(lockMaxRetries)*lockRetryDelay,
 	)
 }
 

filelock_test.go

@@ -40,7 +40,7 @@ func TestConcurrentLocks(t *testing.T) {
 	var mu sync.Mutex
 	concurrent := 0
 
-	for i := 0; i < goroutines; i++ {
+	for i := range goroutines {
 		wg.Add(1)
 		go func(idx int) {
 			defer wg.Done()

main.go

@@ -157,7 +157,7 @@ func getEnv(key, defaultValue string) string {
 // validateServerURL validates that the server URL is properly formatted
 func validateServerURL(rawURL string) error {
 	if rawURL == "" {
-		return fmt.Errorf("server URL cannot be empty")
+		return errors.New("server URL cannot be empty")
 	}
 
 	u, err := url.Parse(rawURL)
@@ -170,7 +170,7 @@ func validateServerURL(rawURL string) error {
 	}
 
 	if u.Host == "" {
-		return fmt.Errorf("URL must include a host")
+		return errors.New("URL must include a host")
 	}
 
 	return nil
@@ -182,12 +182,12 @@ type ErrorResponse struct {
 }
 
 // ErrRefreshTokenExpired indicates that the refresh token has expired or is invalid
-var ErrRefreshTokenExpired = fmt.Errorf("refresh token expired or invalid")
+var ErrRefreshTokenExpired = errors.New("refresh token expired or invalid")
 
 // validateTokenResponse validates the OAuth token response
 func validateTokenResponse(accessToken, tokenType string, expiresIn int) error {
 	if accessToken == "" {
-		return fmt.Errorf("access_token is empty")
+		return errors.New("access_token is empty")
 	}
 
 	if len(accessToken) < 10 {
@@ -330,7 +330,7 @@ func requestDeviceCode(ctx context.Context) (*oauth2.DeviceAuthResponse, error)
 
 	req, err := http.NewRequestWithContext(
 		reqCtx,
-		"POST",
+		http.MethodPost,
 		serverURL+"/oauth/device/code",
 		strings.NewReader(data.Encode()),
 	)
@@ -491,21 +491,20 @@ func pollForTokenWithProgress(
 						case "slow_down":
 							// Server requests slower polling - increase interval
 							backoffMultiplier *= 1.5
-							newInterval := time.Duration(float64(pollInterval) * backoffMultiplier)
-							if newInterval > 60*time.Second {
-								newInterval = 60 * time.Second // Cap at 60 seconds
-							}
-							pollInterval = newInterval
+							pollInterval = min(
+								time.Duration(float64(pollInterval)*backoffMultiplier),
+								60*time.Second,
+							)
 							pollTicker.Reset(pollInterval)
 							continue
 
 						case "expired_token":
 							fmt.Println()
-							return nil, fmt.Errorf("device code expired, please restart the flow")
+							return nil, errors.New("device code expired, please restart the flow")
 
 						case "access_denied":
 							fmt.Println()
-							return nil, fmt.Errorf("user denied authorization")
+							return nil, errors.New("user denied authorization")
 
 						default:
 							fmt.Println()
@@ -558,7 +557,7 @@ func exchangeDeviceCode(
 
 	req, err := http.NewRequestWithContext(
 		reqCtx,
-		"POST",
+		http.MethodPost,
 		tokenURL,
 		strings.NewReader(data.Encode()),
 	)
@@ -623,7 +622,9 @@ func verifyToken(ctx context.Context, accessToken string) error {
 	reqCtx, cancel := context.WithTimeout(ctx, tokenVerificationTimeout)
 	defer cancel()
 
-	req, err := http.NewRequestWithContext(reqCtx, "GET", serverURL+"/oauth/tokeninfo", nil)
+	req, err := http.NewRequestWithContext(
+		reqCtx, http.MethodGet, serverURL+"/oauth/tokeninfo", nil,
+	)
 	if err != nil {
 		return fmt.Errorf("failed to create request: %w", err)
 	}
@@ -666,7 +667,7 @@ func loadTokens() (*TokenStorage, error) {
 	}
 
 	if storageMap.Tokens == nil {
-		return nil, fmt.Errorf("no tokens found in token file")
+		return nil, errors.New("no tokens found in token file")
 	}
 
 	// Look up token for current client_id
@@ -755,7 +756,7 @@ func refreshAccessToken(ctx context.Context, refreshToken string) (*TokenStorage
 
 	req, err := http.NewRequestWithContext(
 		reqCtx,
-		"POST",
+		http.MethodPost,
 		serverURL+"/oauth/token",
 		strings.NewReader(data.Encode()),
 	)
@@ -840,7 +841,9 @@ func makeAPICallWithAutoRefresh(ctx context.Context, storage *TokenStorage) erro
 	reqCtx, cancel := context.WithTimeout(ctx, tokenVerificationTimeout)
 	defer cancel()
 
-	req, err := http.NewRequestWithContext(reqCtx, "GET", serverURL+"/oauth/tokeninfo", nil)
+	req, err := http.NewRequestWithContext(
+		reqCtx, http.MethodGet, serverURL+"/oauth/tokeninfo", nil,
+	)
 	if err != nil {
 		return fmt.Errorf("failed to create request: %w", err)
 	}
@@ -877,7 +880,9 @@ func makeAPICallWithAutoRefresh(ctx context.Context, storage *TokenStorage) erro
 		retryCtx, retryCancel := context.WithTimeout(ctx, tokenVerificationTimeout)
 		defer retryCancel()
 
-		req, err = http.NewRequestWithContext(retryCtx, "GET", serverURL+"/oauth/tokeninfo", nil)
+		req, err = http.NewRequestWithContext(
+			retryCtx, http.MethodGet, serverURL+"/oauth/tokeninfo", nil,
+		)
 		if err != nil {
 			return fmt.Errorf("failed to create retry request: %w", err)
 		}