You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: succeed_matcher.go
    path of file: ./repos/kubernetes/vendor/github.com/onsi/gomega/matchers
    
    the code of the file until where you have to start completion: package matchers

import (
	"errors"
	"fmt"

	"github.com/onsi/gomega/format"
)

type formattedGomegaError interface {
	FormattedGomegaError() string
}

type
    
func (matcher *SucceedMatcher) FailureMessage(actual interface{}) (message string) {
	var fgErr formattedGomegaError
	if errors.As(actual.(error), &fgErr) {
		return fgErr.FormattedGomegaError()
	}
	return fmt.Sprintf("Expected success, but got an error:\n%s", format.Object(actual, 1))
}