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: backend.go
    path of file: ./repos/gnark/backend
    
    the code of the file until where you have to start completion: // Copyright 2020 ConsenSys AG
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the L
    
func NewProverConfig(opts ...ProverOption) (ProverConfig, error) {
	opt := ProverConfig{
		// we cannot initialize HashToFieldFn here as we use different domain
		// separation tags for PLONK and Groth16
		ChallengeHash:  sha256.New(),
		KZGFoldingHash: sha256.New(),
	}
	for _, option := range opts {
		if err := option(&opt); err != nil {
			return ProverConfig{}, err
		}
	}
	return opt, nil
}