file: Add lock to not conflict with async tasks

internal/file/file.go

@@ -5,12 +5,17 @@ import (
 	"io"
 	"os"
 	"path/filepath"
+	"sync"
 
 	"github.com/zyedidia/micro/v2/internal/util"
 	"golang.org/x/text/encoding"
 	"golang.org/x/text/transform"
 )
 
+var (
+	lock sync.Mutex
+)
+
 type OptionalWriteSteps struct {
 	PreWrite  func() (io.WriteCloser, encoding.Encoding, error)
 	PostWrite func() error
@@ -22,6 +27,8 @@ type OptionalWriteSteps struct {
 func Overwrite(name string, write func(io.Writer) error, optSteps ...OptionalWriteSteps) (err error) {
 	var writeCloser io.WriteCloser
 	enc := encoding.Nop
+	lock.Lock()
+	defer lock.Unlock()
 	for _, optional := range optSteps {
 		tmpEnc := encoding.Nop
 		writeCloser, tmpEnc, err = optional.PreWrite()