What are the rules for working with interfaces in Go?

In Go, interfaces play a key role, and when working with them, it is important to consider a few rules:

• Interfaces should be small and specialized. It is better to create an interface with one or two methods to increase flexibility.
• Use interfaces to define behavior, not to describe data.
• Do not declare interface methods with redundant parameters — the interface should be simple and understandable.
• In Go, interface implementation is implicit: a type satisfies an interface if it implements its methods. This allows for easy substitution of implementations.
• For testing, it is convenient to create interfaces to replace real implementations with mocks.

Example of an interface with one method:

package main

import "fmt"

type Reader interface {
    Read(p []byte) (n int, err error)
}

func main() {
    var r Reader
    // r can be any type that implements Read
    fmt.Println(r)
}

This approach facilitates code extension and maintenance.