A map that supports default values.
import (
"fmt"
"github.com/spenserblack/go-defaultmap"
)
m := defaultmap.NewMap[string](func() string { return "I'm the default!" })
m.Insert("exists", "Hello, World!")
fmt.Println(m.Get("exists")) // Hello, World!
fmt.Println(m.Get("doesn't exist")) // I'm the default!
fmt.Println(m.GetOr("also doesn't exist", "I'm a one-time default!")) // I'm a one-time default!