go-functional-options

The functional options pattern configures Go structs by passing optional parameters as closure functions, keeping constructors readable and maintainable. This approach handles optional parameters with validation and defaults instead of using complex parameter lists.

The functional options pattern is a design technique for flexible Go struct initialization. You should use it when creating configurable types like database connections needing optional parameters such as timeout duration, connection pool size, or logger instances.

Yes, the functional options pattern supports Go 1.25 generics for advanced reusability. Generic implementations require Go 1.25+ to leverage closure-based or interface-based patterns for application or library code configuration.

You implement validation directly within Go functional option functions by returning errors from the closures. This integrates robust error checking into the configuration process, ensuring optional parameters meet requirements before struct initialization completes.

The best way to set defaults and optional parameters for a Go constructor is using composable functional options. This pattern applies closure-based or interface-based configuration to provide flexible initialization with built-in validation and default values.

You need Go 1.25+ specifically for generic implementations of functional options. Standard closure-based or interface-based functional options patterns for struct configuration work without this version requirement for application or library code.