type Strategy interface {
    Operate()
}

type ImplOne struct{}

func (impl *ImplOne) Operate() {
    fmt.Println("this is the first implementation")
}

type ImplTwo struct{}

func (impl *ImplTwo) Operate() {
    fmt.Println("this is the second implementation")
}

type Context struct {
    strategy Strategy
}

func NewContext(strategy Strategy) *Context {
    return &Context{strategy: strategy}
}

func (context *Context) SetStrategy(strategy Strategy) {
    context.strategy = strategy
}

func (context *Context) ExecuteStrategy() {
    context.strategy.Operate()
}

func TestContext_ExecuteStrategy(t *testing.T) {
    context := NewContext(&ImplOne{})
    context.ExecuteStrategy()
    
    context.SetStrategy(&ImplTwo{})
    context.ExecuteStrategy()
}