fix: resolve all golangci-lint errors

Fix multiple linter issues to pass CI/CD checks:
- errcheck: Add error handling for w.Write(), cfg.ClearTokens(), and buf.ReadFrom() calls
- unused: Remove unused variable 'nl' in cmd/image.go
- ineffassign: Fix ineffectual assignment to contentType in detectContentType()
- staticcheck SA1019: Replace deprecated netErr.Temporary() with timeout check
- staticcheck SA4020: Reorder switch cases to avoid unreachable code (interface{} matches all)
- staticcheck SA9003: Clarify empty branch comment in retry delay logic

🤖 Generated with [Claude Code]

Co-Authored-By: Claude <noreply@anthropic.com>

Author: agb-cloud

cmd/image.go

@@ -40,9 +40,6 @@ func getNewline() string {
 	return "\n"
 }
 
-// nl is a convenience variable for newline
-var nl = getNewline()
-
 var ImageCmd = &cobra.Command{
 	Use:     "image",
 	Short:   "Manage images",

internal/auth/auth.go

@@ -56,7 +56,11 @@ func StartCallbackServer(ctx context.Context, port string) (string, error) {
 		// Return success page
 		w.Header().Set("Content-Type", "text/html")
 		w.WriteHeader(http.StatusOK)
-		w.Write([]byte(GetSuccessHTML()))
+		if _, writeErr := w.Write([]byte(GetSuccessHTML())); writeErr != nil {
+			// Log the error but don't fail the authentication
+			// The code has already been captured successfully
+			err = fmt.Errorf("warning: failed to write success page: %w", writeErr)
+		}
 
 		// Delay server close to ensure browser receives the success page
 		go func() {

internal/auth/token_manager.go

@@ -44,13 +44,13 @@ func RefreshTokenIfNeeded(ctx context.Context) error {
 		cfg.Token.SessionId)
 	if err != nil {
 		// If refresh fails, clear the tokens
-		cfg.ClearTokens()
+		_ = cfg.ClearTokens() // Ignore error as we're already returning the refresh error
 		return fmt.Errorf("use 'agbcloud-cli login' to reauthenticate: %w", err)
 	}
 
 	if !response.Success {
 		// If refresh fails, clear the tokens
-		cfg.ClearTokens()
+		_ = cfg.ClearTokens() // Ignore error as we're already returning the refresh error
 		return fmt.Errorf("use 'agbcloud-cli login' to reauthenticate: refresh failed with code %s", response.Code)
 	}
 

internal/client/client.go

@@ -272,16 +272,15 @@ func setBody(body interface{}, contentType string) (bodyBuf *bytes.Buffer, err e
 func detectContentType(body interface{}) string {
 	contentType := "text/plain; charset=utf-8"
 	switch body.(type) {
-	case map[string]interface{}, []interface{}, interface{}:
-		contentType = "application/json; charset=utf-8"
 	case string:
-		contentType = "text/plain; charset=utf-8"
+		// Already set to text/plain by default, no need to reassign
+	case []byte:
+		contentType = http.DetectContentType(body.([]byte))
+	case map[string]interface{}, []interface{}:
+		contentType = "application/json; charset=utf-8"
 	default:
-		if b, ok := body.([]byte); ok {
-			contentType = http.DetectContentType(b)
-		} else {
-			contentType = "application/json; charset=utf-8"
-		}
+		// For any other type, assume JSON
+		contentType = "application/json; charset=utf-8"
 	}
 
 	return contentType

internal/client/retry.go

@@ -76,8 +76,10 @@ func IsRetryableError(err error) bool {
 	}
 
 	// Check for specific error types
+	// Note: netErr.Temporary() is deprecated since Go 1.18
+	// We rely on string matching and timeout checks instead
 	if netErr, ok := err.(net.Error); ok {
-		return netErr.Temporary() || netErr.Timeout()
+		return netErr.Timeout()
 	}
 
 	// Check for syscall errors
@@ -189,7 +191,7 @@ func (r *RetryableHTTPClient) Do(req *http.Request) (*http.Response, error) {
 
 		select {
 		case <-time.After(delay):
-			// Continue to next attempt
+			// Delay elapsed, continue to next attempt
 		case <-req.Context().Done():
 			return nil, req.Context().Err()
 		}

test/unit/cpu_memory_validation_test.go

@@ -24,7 +24,7 @@ func captureStderrCPU(f func()) string {
 	os.Stderr = oldStderr
 
 	var buf bytes.Buffer
-	buf.ReadFrom(r)
+	_, _ = buf.ReadFrom(r) // Ignore errors in test helper
 	return buf.String()
 }
 

test/unit/error_message_formatting_test.go

@@ -26,7 +26,7 @@ func captureStderrErr(f func()) string {
 	os.Stderr = oldStderr
 
 	var buf bytes.Buffer
-	buf.ReadFrom(r)
+	_, _ = buf.ReadFrom(r) // Ignore errors in test helper
 	return buf.String()
 }
 

test/unit/image_cmd_test.go

@@ -28,7 +28,7 @@ func captureStderr(f func()) string {
 	os.Stderr = oldStderr
 
 	var buf bytes.Buffer
-	buf.ReadFrom(r)
+	_, _ = buf.ReadFrom(r) // Ignore errors in test helper
 	return buf.String()
 }