Tidy up codebase to deal with new linter errors

[Dan7-7-7]

The following came from github copilot's analysis of #166:

The failing job encountered several linter errors. The most critical are due to error return values from file Close operations not being checked in your Go code (errcheck), a malformed test name (govet), capitalization of error strings (staticcheck), and a couple of staticcheck suggestions. Here’s how you can fix them:

---

1. Check Error Returns for File Close Operations

In cmd/foreach/foreach.go, you should check errors when deferring .Close() on files. Change:

defer successfulReposFile.Close()
defer failedReposFile.Close()

to:

defer func() {
    if err := successfulReposFile.Close(); err != nil {
        logger.Warnf("Failed to close successfulReposFile: %v", err)
    }
}()
defer func() {
    if err := failedReposFile.Close(); err != nil {
        logger.Warnf("Failed to close failedReposFile: %v", err)
    }
}()

Apply the same pattern for:

defer reposFile.Close()
defer logs.Close()

Replace all simple defer file.Close() with a defer func(){ ... }() as above.

---

2. Test Files: Check Error Returns for os.RemoveAll

In cmd/foreach/foreach_test.go, update:

defer os.RemoveAll("mock_output")

to:

defer func() {
    if err := os.RemoveAll("mock_output"); err != nil {
        t.Logf("Failed to remove mock_output: %v", err)
    }
}()

Do this for all similar occurrences.

---

3. Test Name Capitalization (govet)

In internal/github/util_test.go, rename:

func TestuserHasPushPermissionReturnsErrorForInvalidJSON(t *testing.T)

to:

func TestUserHasPushPermissionReturnsErrorForInvalidJSON(t *testing.T)

---

4. Error String Capitalization (staticcheck)

In cmd/foreach/foreach.go:

return errors.New("Use -- to separate command")

should be:

return errors.New("use -- to separate command")

---

5. Prefer fmt.Fprintf Over WriteString(fmt.Sprintf(...)) (staticcheck)

Instead of:

_, _ = successfulReposFile.WriteString(fmt.Sprintf("# This file contains ..."))

Use:

fmt.Fprintf(successfulReposFile, "# This file contains ...")

Do the same for failedReposFile.

---

6. Deprecation Warning for io/ioutil (staticcheck)

In cmd/init/init_test.go, replace:

import "io/ioutil"
...
readmeContents, err := ioutil.ReadFile("foo/README.md")

with:

import "os"
...
readmeContents, err := os.ReadFile("foo/README.md")

---

Summary

• Check error returns for all file .Close() and os.RemoveAll() operations.
• Fix test function naming to start with Test.
• Use lowercase for the start of error messages.
• Replace WriteString(fmt.Sprintf(...)) with fmt.Fprintf.
• Use os.ReadFile instead of ioutil.ReadFile.

Apply these changes and rerun your linter/job. These fixes should resolve all the linter errors shown in the logs. If you need the specific code snippets for any file, let me know!