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: plugin.go
    path of file: ./repos/chainlink/core/services/ocr2/plugins/mercury
    
    the code of the file until where you have to start completion: package mercury

import (
	"encoding/json"
	"fmt"
	"os/exec"

	"github.com/pkg/errors"

	libocr2 "github.com/smartcontractkit/libocr/offchainreporting2plus"
	"github.com/smartcontractkit/libocr/offchainreporting2plus/ocr3types"

	relaymercuryv1 "github.com/smartcontractkit/chainlink-data-streams/mercury/v1"
	relaymercuryv2 "github.com/smartcontractkit/cha
    
func initLoop(cmd string, cfg Config, feedID utils.FeedID, lggr logger.Logger) (func() *exec.Cmd, loop.GRPCOpts, logger.Logger, error) {
	lggr.Debugw("Initializing Mercury loop", "command", cmd)
	mercuryLggr := lggr.Named(fmt.Sprintf("MercuryV%d", feedID.Version())).Named(feedID.String())
	envVars, err := plugins.ParseEnvFile(env.MercuryPlugin.Env.Get())
	if err != nil {
		return nil, loop.GRPCOpts{}, nil, fmt.Errorf("failed to parse mercury env file: %w", err)
	}
	cmdFn, opts, err := cfg.RegisterLOOP(plugins.CmdConfig{
		ID:  mercuryLggr.Name(),
		Cmd: cmd,
		Env: envVars,
	})
	if err != nil {
		return nil, loop.GRPCOpts{}, nil, fmt.Errorf("failed to register loop: %w", err)
	}
	return cmdFn, opts, mercuryLggr, nil
}