How to create custom error types that implement the error interface in Go?

To create custom error types that implement the error interface in Go, you need to define a new type that satisfies the error interface. Here's an example:

package main

import (
	"fmt"
)

type MyError struct {
	Code    int
	Message string
}

func (e *MyError) Error() string {
	return fmt.Sprintf("Error: %d - %s", e.Code, e.Message)
}

func main() {
	err := &MyError{Code: 500, Message: "Internal Server Error"}
	fmt.Println(err.Error())
}

In the above code:

We define a new struct MyError with two fields Code and Message.
We implement the Error() method for the MyError type. This method satisfies the error interface by returning a string representation of the error.
In the main() function, we create an instance of MyError and print the error by calling err.Error(), which implicitly calls the Error() method we defined.

The output will be: "Error: 500 - Internal Server Error".

By creating custom error types like this, you can provide more detailed and meaningful error messages in your Go programs.