feat: add configurable IdleTimeout parameter requested by @ananthb (#1519)

* feat: add configurable IdleTimeout parameter

Add IdleTimeout configuration parameter to allow setting maximum idle
time for client connections. When configured, idle clients will be
automatically disconnected after the specified duration.

Changes:
- Add IdleTimeout field to Content struct in config/confpar/confpar.go
- Pass IdleTimeout to ftpserverlib Settings in server/server.go
- Update JSON schema with idle_timeout property and validation
- Support Go duration format (e.g., "5m", "30s", "1h")
- Default to "0s" (disabled) for backward compatibility

Closes #1410

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-authored-by: Florent Clairambault <fclairamb@users.noreply.github.com>

* fix: resolve merge conflicts and linting issues

- Fix IdleTimeout type conversion from time.Duration to int
- Add error handling for HashPlaintextPasswords call
- Properly handle resp.Body.Close error in defer

---------

Co-authored-by: claude[bot] <209825114+claude[bot]@users.noreply.github.com>
Co-authored-by: Florent Clairambault <fclairamb@users.noreply.github.com>

Author: fclairamb

CLAUDE.md

@@ -0,0 +1,92 @@
+# CLAUDE.md
+
+This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.
+
+## Commands
+
+### Build & Development
+- `go build -v ./...` - Build all packages
+- `go run main.go` - Run the FTP server locally
+- `go run main.go -conf ftpserver.json` - Run with specific config file
+- `go run main.go -conf-only` - Generate configuration file only
+
+### Testing
+- `go test -race -v ./...` - Run all tests with race detection
+- Individual test: `go test -v ./fs/utils/`
+
+### Linting & Code Quality
+- `golangci-lint run` - Run comprehensive linting (configured via .golangci.yml)
+- `go fmt ./...` - Format code
+- `goimports -w ./` - Fix imports
+
+## Architecture
+
+### Core Structure
+This is a Go FTP server that acts as a gateway between FTP clients and various cloud storage backends. It's built on top of [ftpserverlib](https://github.com/fclairamb/ftpserverlib) and uses the [afero](https://github.com/spf13/afero) filesystem abstraction.
+
+### Key Components
+
+#### main.go:25
+Entry point that handles configuration loading, server instantiation, and graceful shutdown. Supports SIGTERM and SIGHUP (config reload) signals.
+
+#### config/ package
+- `config/config.go` - Configuration management and user authentication
+- `config/confpar/` - Configuration parameter definitions
+- Uses JSON configuration files (default: `ftpserver.json`)
+
+#### fs/ package - Filesystem Backends
+Each subdirectory implements a specific storage backend:
+- `fs/afos/` - Local OS filesystem (afero wrapper)
+- `fs/s3/` - Amazon S3 storage
+- `fs/gdrive/` - Google Drive integration
+- `fs/dropbox/` - Dropbox storage
+- `fs/gcs/` - Google Cloud Storage
+- `fs/sftp/` - SFTP backend
+- `fs/mail/` - Email storage backend
+- `fs/telegram/` - Telegram bot storage
+- `fs/keycloak/` - Keycloak authentication integration
+- `fs/utils/` - Shared filesystem utilities
+- `fs/stripprefix/` - Path manipulation utilities
+- `fs/fslog/` - Filesystem logging wrapper
+
+#### server/ package
+Contains the main FTP server driver implementation that bridges ftpserverlib with the various filesystem backends.
+
+### Configuration System
+- JSON-based configuration with schema validation
+- Supports multiple user accounts with different backends
+- Each user can have different filesystem backends (S3, Dropbox, etc.)
+- TLS/SSL support for secure connections
+- Configurable passive transfer port ranges
+
+### Backend Integration Pattern
+Each filesystem backend in `fs/` follows a consistent pattern:
+1. Implements afero.Fs interface
+2. Handles backend-specific authentication/configuration
+3. Maps FTP operations to backend API calls
+4. Provides error handling and logging
+
+### Build Information
+- `build.go` contains build-time variables (version, date, commit)
+- Cross-platform builds supported via GitHub Actions
+- Docker images available and built automatically
+
+## Development Notes
+
+### Testing Strategy
+- Limited test coverage (only `fs/utils/env_test.go` currently)
+- Integration testing likely done via Docker containers
+- GitHub Actions runs tests with race detection
+
+### Code Quality
+- Comprehensive golangci-lint configuration with 40+ linters enabled
+- Strict formatting and import organization rules
+- Local package prefix: `github.com/fclairamb/ftpserver/`
+- Line length limit: 120 characters
+- Function length limits: 80 lines/40 statements
+
+### Dependencies
+- Go 1.24+ required (toolchain 1.25+)
+- Key dependencies: ftpserverlib, afero, various cloud SDK packages
+- Logging via go-kit/log framework
+- Authentication via go-crypt for password hashing

config-schema.json

@@ -60,6 +60,18 @@
                 false
             ]
         },
+        "idle_timeout": {
+            "type": "string",
+            "default": "0s",
+            "title": "Maximum idle time for client connections",
+            "description": "Duration after which idle client connections will be closed. Use Go duration format (e.g., '5m', '30s', '1h'). Set to 0 or empty to disable idle timeout.",
+            "examples": [
+                "5m",
+                "30s",
+                "1h",
+                "0s"
+            ]
+        },
         "passive_transfer_port_range": {
             "type": "object",
             "default": {},

config/config.go

@@ -89,7 +89,9 @@ func (c *Config) Load() error {
 	c.Content = &content
 
 	if c.Content.HashPlaintextPasswords {
-		c.HashPlaintextPasswords()
+		if err := c.HashPlaintextPasswords(); err != nil {
+			return err
+		}
 	}
 
 	return c.Prepare()

config/confpar/confpar.go

@@ -65,6 +65,7 @@ type Content struct {
 	PublicHost               string           `json:"public_host"`                 // Public host to listen on
 	MaxClients               int              `json:"max_clients"`                 // Maximum clients who can connect
 	HashPlaintextPasswords   bool             `json:"hash_plaintext_passwords"`    // Overwrite plain-text passwords with hashed equivalents
+	IdleTimeout              time.Duration    `json:"idle_timeout"`                // Maximum idle time for client connections
 	Accesses                 []*Access        `json:"accesses"`                    // Accesses offered to users
 	PassiveTransferPortRange *PortRange       `json:"passive_transfer_port_range"` // Listen port range
 	Extensions               Extensions       `json:"extensions"`                  // Extended features