What does the Error interface signify in the context of error handling?

In Go, the Error interface defines a type for error handling and contains a single method:

type error interface {
    Error() string
}

This method returns a string description of the error. Any type implementing this method is considered an error and can be used with error handling constructs, such as if err != nil.

This approach allows creating custom error types with additional information while maintaining compatibility with the general interface. For example:

type MyError struct {
    Msg string
}

func (e MyError) Error() string {
    return e.Msg
}
}

func doSomething() error {
    return MyError{Msg: "something went wrong"}
}

Thus, the Error interface is the standard way of passing and handling errors in Go.