gofmt check fails if go.mod and go.sum are not in the root directory

[gchappel]

Describe the bug
The gofmt check fails if Go code is stored in a subdirectory of the repository:

gofmt....................................................................Failed
- hook id: gofmt
- exit code: 1

go: cannot find main module, but found .git/config in /Users/gchappel/code/sample-directory
	to create a module there, run:
	go mod init

To Reproduce

• Create an empty directory
• git init .
• Configure .pre-commit-config.yaml with the Gruntwork pre-commit repo and enable the gofmt hook
• Create a subdirectory
• In this subdirectory run go mod init test
• In the subdirectory write a deliberately-malformed Go file, for example using spaces instead of tabs:

package main

import (
  "fmt" // this line starts with two spaces
)

func main() {
  fmt.Println("test")  // this line starts with two spaces
}

• git add . to add the Go code and the .pre-commit-config.yaml to the staging area
• run pre-commit run gofmt
• see error

Expected behavior
The malformed Go file has its spaces replaced with tabs

Nice to have

• Terminal output
• Screenshots

Additional context
Add any other context about the problem here.