Needed to make some replacements that were a bit much for sed, and didn't want to use awk, perl, or python.

replacestuff.go

package main

import (
	"fmt"
	"io/ioutil"
	"log"
	"os"
	"path/filepath"
	"regexp"
	"strings"
)

func main() {
	filepath.Walk(".", func(path string, info os.FileInfo, err error) error {
		if info.IsDir() {
			return nil
		}

		if strings.Contains(path, "/vendor/") {
			return nil
		}

		if filepath.Ext(path) != ".go" {
			return nil
		}

		if info.Name() == "fixtests.go" {
			return nil
		}

		rawSrc, err := ioutil.ReadFile(path)
		if err != nil {
			panic(err)
		}
		src := string(rawSrc)

		regexOne := regexp.MustCompile(`mockController := gomock\.NewController\(t\)`)

		if !regexOne.MatchString(src) {
			return nil
		}

		log.Println(path)

		firstReplacementSrc := regexOne.ReplaceAllLiteralString(
			src,
			fmt.Sprintf("mockController := gomock.NewController(t)\n\tdefer mockController.Finish()"))

		regexTwo := regexp.MustCompile(`defer mockController\.Finish\(\)\n\tdefer mockController.Finish\(\)`)
		secondReplacementSrc := regexTwo.ReplaceAllLiteralString(
			firstReplacementSrc,
			fmt.Sprintf("defer mockController.Finish()"))

		err = ioutil.WriteFile(path, []byte(secondReplacementSrc), 0777)

		if err != nil {
			panic(err)
		}
		return nil
	})
}