ā† Back to Learning
June 10, 2026 Go

Go Generics & Type Constraints

Go Generics Type Safety

Mastered Go generics syntax and type constraints, enabling reusable algorithms while maintaining compile-time type safety.

Key Learnings:

  • Type Parameters: Written in square brackets (e.g., [T any]) before parameter lists.
  • Constraints: Define what types are allowed. Standard constraints are in the golang.org/x/exp/constraints package (like Ordered for < and > comparisons).
  • The any constraint: An alias for interface{}.
  • The comparable constraint: A built-in interface that allows operations like == and !=.
  • Underlying types: Using the ~ symbol (e.g., ~int matches any custom type whose underlying type is int).

Real-World Code Example

package generics

// MapKeys returns a slice of all keys in a map.
// Keys must be comparable, and values can be any type.
func MapKeys[K comparable, V any](m map[K]V) []K {
    keys := make([]K, 0, len(m))
    for k := range m {
        keys = append(keys, k)
    }
    return keys
}

This utility function works on maps of strings to ints, ints to floats, or any comparable key, eliminating duplicate helper functions!