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README.md

Required Flags Demo

This demo shows how to use FlashFlags' required flags functionality, including flag dependencies.

Features Demonstrated

  • Required Flags: Flags that must be provided by the user
  • Flag Dependencies: Flags that are required only when other flags are set
  • Error Handling: Proper validation and user-friendly error messages
  • Help Integration: Professional help output with grouped flags

Running the Demo

Show Help

go run main.go --help

Missing Required Flags (will fail)

go run main.go --host localhost --port 3000 # Error: required flag --api-key not provided

Provide Required Flags (will succeed)

go run main.go --api-key "your-secret-key" --db-url "postgres://user@localhost/db"

TLS Example with Dependencies

# This will fail because TLS is enabled but cert/key are missing go run main.go --api-key "key123" --db-url "postgres://user@localhost/db" --enable-tls # This will succeed - TLS enabled with required cert and key go run main.go \ --api-key "your-secret-key" \ --db-url "postgres://user:pass@localhost/mydb" \ --db-password "dbpass123" \ --enable-tls \ --tls-cert "/path/to/cert.pem" \ --tls-key "/path/to/key.pem" \ --host "0.0.0.0" \ --port 8443

Code Structure

Required Flags

The demo marks these flags as absolutely required:

  • --api-key: Authentication token
  • --db-url: Database connection string

Conditional Requirements (Dependencies)

These flags are required only when their dependencies are set:

  • --tls-cert and --tls-key: Required when --enable-tls is true
  • --db-password: Required when --db-url is provided

Implementation Details

// Mark a flag as required fs.SetRequired("api-key") // Set up dependencies fs.SetDependencies("tls-cert", "enable-tls") fs.SetDependencies("tls-key", "enable-tls")

Error Messages

FlashFlags provides clear error messages for validation failures:

Configuration Error: required flag --api-key not provided Run with --help to see all available options

Security Features

The demo includes security best practices:

  • Secret Masking: API keys and passwords are masked in output
  • Connection String Protection: Database URLs are partially hidden
  • Clear Separation: Required vs optional flags are clearly documented

Real-World Usage

This pattern is common in production applications where:

  • API keys are mandatory for external service access
  • Database connections require proper configuration
  • TLS setup needs both certificate and key files
  • Different deployment environments have different requirements

The required flags feature ensures your application fails fast with clear error messages rather than running with incomplete configuration.

flash-flags • an AGILira library