configuration-management - SKILL.md Agent Skill

name: configuration-management description: Use when adding or changing NanoProxy configuration — the env-driven struct config in pkg/config (caarlos0/env/v10), struct-tag defaults, and validation. Note real env vars (ADDR, ADDR_HTTP, TOR_ENABLED, USER_STORE_PATH).

Configuration Management

Expertise in managing environment-based configuration for NanoProxy using struct-based parsing and environment variables.

When to use this skill

Setting up NanoProxy configuration
Adding new configuration options
Handling environment variables
Implementing configuration validation
Managing configuration defaults

Expertise areas

Struct-based configuration parsing
Environment variable handling
Default values and validation
Type conversion for config values
Runtime configuration usage

Key files

pkg/config/config.go - Configuration implementation (uses caarlos0/env/v10)
nanoproxy.go - Main entry point with config usage

Notes specific to NanoProxy

Config is env-driven only (no JSON/YAML files). The SOCKS5 listen address is ADDR (default :1080) and the HTTP proxy listen address is ADDR_HTTP (default :8080). Credentials are stored at USER_STORE_PATH (BoltDB).
Always confirm the actual env tags in pkg/config/config.go before documenting or referencing them.

Common tasks

Defining configuration structure

Use struct tags to define configuration from environment variables.

Parsing environment variables

Use the caarlos0/env library to automatically parse the struct from the environment.

Setting defaults

Define default values in struct tags via envDefault.

Validating configuration

Validate configuration values after parsing.

Example patterns

Configuration struct

type Config struct {
    Addr           string `env:"ADDR" envDefault:":1080"`
    AddrHTTP       string `env:"ADDR_HTTP" envDefault:":8080"`
    TOREnabled     bool   `env:"TOR_ENABLED" envDefault:"false"`
    UserStorePath  string `env:"USER_STORE_PATH"`
    LogLevel       string `env:"LOG_LEVEL" envDefault:"info"`
}

Parsing configuration

cfg := &Config{}
if err := env.Parse(cfg); err != nil {
    logger.Fatal().Err(err).Msg("failed to parse config")
}

// Validate
if cfg.Addr == "" && cfg.AddrHTTP == "" {
    logger.Fatal().Msg("at least one proxy address must be configured")
}

Testing approach

Test with various environment variable combinations
Test default value usage
Test type conversion
Test validation logic
Test missing required values
Test invalid value formats
Test environment variable overrides

Performance considerations

Parse config once at startup
Cache config values
Avoid frequent environment variable reads

Security considerations

Never log sensitive values (passwords, secrets)
Validate all config values
Use environment variables for secrets
Document required vs optional values

References

caarlos0/env GitHub repository
Go struct tags documentation

Related skills

credential-management - Handling persisted proxy users and admin-auth flows
socks5-protocol - Using config in SOCKS5 setup
http-proxy - Using config in HTTP proxy setup