Example of checking whether a struct fulfills an interface dynamically at runtime

interface_check.go

package main

import (
	"fmt"
	"reflect"
)

type A interface {
	Set(string) error
}

type B interface {
	Get() string
}

type C struct {
	hello string
}
func (c *C) Set(s string) error {
	return nil
}

func main() {
	c := &C{
		hello: "world",
	}
	
	// Force interface check at compile type
	// C implements A
	var _ A = (*C)(nil)
	
	var ok bool
	// Compile type check with reflection
	dest := reflect.ValueOf(c)
	_, ok = dest.Interface().(A)
	fmt.Printf("c implements A - %v\n", ok)
	
	_, ok = dest.Interface().(B)
	fmt.Printf("c implements B - %v\n", ok)
}