Custom constraint golang 1.18 generics

main.go

package main

import (
	"fmt"
)

type Contstraint[I, O any] interface {
	Process(in I) (out O)
}

func Print[I, O any](c Contstraint[I, O], in I) {
	fmt.Println(c.Process(in))
}

type Custom struct {}

func (c Custom) Process(a int) (b string) {
	return fmt.Sprintf("%d", a) + "."
}

func main() {
	c := Custom{}
	Print[int, string](c, 123)
}