Example of type assertion failure

type_assertion.go

package main

import (
	"fmt"
)

type Aer interface {
	DoA()
}

type Ber interface {
	DoB()
}

type A bool

func (a A) DoA() {
	fmt.Println("A.DoA")
}

func main() {
	defer func() {
		if x := recover(); x != nil {
			fmt.Println(x)
		}
	}()

	var a A
	var aer Aer
	aer = a
	aer.DoA()

	var ber Ber
	// interface conversion failed
	ber = aer.(Ber)
	ber.DoB()
}