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: gen.go
    path of file: ./repos/goa/cmd/goa
    
    the code of the file until where you have to start completion: package main

import (
	"errors"
	"fmt"
	"go/build"
	"go/parser"
	"go/token"
	"os"
	"os/exec"
	"path/filepath"
	"regexp"
	"runtime"
	"strconv"
	"strings"

	"goa.design/goa/v3/codegen"
	"golang.org/x/tools/go/packages"
)

// Generator is the code generation management data structure.
type Generator struct {
	// Command is the name of the command to run.
	Command string

	// DesignPath is the Go import path to the design package.
	DesignPath string

	// Output is the absolute path to the output directory.
	Output string

	
    
func (g *Generator) Compile() error {
	// We first need to go get the generated package to make sure that all
	// dependencies are added to go.sum prior to compiling.
	pkgs, err := packages.Load(&packages.Config{Mode: packages.NeedName}, fmt.Sprintf(".%c%s", filepath.Separator, g.tmpDir))
	if err != nil {
		return err
	}
	if len(pkgs) != 1 {
		return fmt.Errorf("expected to find one package in %s", g.tmpDir)
	}
	if !g.hasVendorDirectory {
		if err := g.runGoCmd("get", pkgs[0].PkgPath); err != nil {
			return err
		}
	}

	err = g.runGoCmd("build", "-o", g.bin)

	// If we're in vendor context we check the error string to see if it's an issue of unsatisfied dependencies
	if err != nil && g.hasVendorDirectory {
		if strings.Contains(err.Error(), "cannot find package") && strings.Contains(err.Error(), "/goa.design/goa/v3/codegen/generator") {
			return errors.New("generated code expected `goa.design/goa/v3/codegen/generator` to be present in the vendor directory, see documentation for more details")
		}
	}

	return err
}