Update Atomic package

Add docstring to fh.sync
Update the code to not use ioutil package.

lib/file/atomic.go

@@ -34,6 +34,7 @@ func WriteAtomicWithPerms(path string, contents []byte, dirPerms, filePerms os.F
 		os.Remove(tempPath)
 		return err
 	}
+	// Commits the current state of the file to disk
 	if err := fh.Sync(); err != nil {
 		fh.Close()
 		os.Remove(tempPath)

lib/file/atomic_test.go

@@ -1,7 +1,6 @@
 package file
 
 import (
-	"io/ioutil"
 	"os"
 	"path/filepath"
 	"testing"
@@ -13,7 +12,7 @@ import (
 // tests that it just writes the file properly. I would love to test this
 // better but I'm not sure how. -mitchellh
 func TestWriteAtomic(t *testing.T) {
-	td, err := ioutil.TempDir("", "lib-file")
+	td, err := os.MkdirTemp("", "lib-file")
 	require.NoError(t, err)
 	defer os.RemoveAll(td)
 
@@ -25,7 +24,7 @@ func TestWriteAtomic(t *testing.T) {
 	require.NoError(t, WriteAtomic(path, expected))
 
 	// Read and verify
-	actual, err := ioutil.ReadFile(path)
+	actual, err := os.ReadFile(path)
 	require.NoError(t, err)
 	require.Equal(t, expected, actual)
 }