Why are interfaces needed in Golang?
<p>In Golang, we use structs with receiver methods. everything is perfect up to here.<br>
I'm not sure what interfaces are, however. We define methods in structs and if we want to implement a method on a struct, we write it anyway again under another struct.<br>
This means that interfaces seem to be just method definitions, taking just extra unneeded space on our page.</p>

<p>Is there any example explaining why I need an interface?</p>