Upgrade server dependencies, manage them with govendor

vendor/github.com/boltdb/bolt/bolt_windows.go

@@ -16,6 +16,8 @@ var (
 )
 
 const (
+	lockExt = ".lock"
+
 	// see https://msdn.microsoft.com/en-us/library/windows/desktop/aa365203(v=vs.85).aspx
 	flagLockExclusive       = 2
 	flagLockFailImmediately = 1
@@ -46,7 +48,16 @@ func fdatasync(db *DB) error {
 }
 
 // flock acquires an advisory lock on a file descriptor.
-func flock(f *os.File, exclusive bool, timeout time.Duration) error {
+func flock(db *DB, mode os.FileMode, exclusive bool, timeout time.Duration) error {
+	// Create a separate lock file on windows because a process
+	// cannot share an exclusive lock on the same file. This is
+	// needed during Tx.WriteTo().
+	f, err := os.OpenFile(db.path+lockExt, os.O_CREATE, mode)
+	if err != nil {
+		return err
+	}
+	db.lockfile = f
+
 	var t time.Time
 	for {
 		// If we're beyond our timeout then return an error.
@@ -62,7 +73,7 @@ func flock(f *os.File, exclusive bool, timeout time.Duration) error {
 			flag |= flagLockExclusive
 		}
 
-		err := lockFileEx(syscall.Handle(f.Fd()), flag, 0, 1, 0, &syscall.Overlapped{})
+		err := lockFileEx(syscall.Handle(db.lockfile.Fd()), flag, 0, 1, 0, &syscall.Overlapped{})
 		if err == nil {
 			return nil
 		} else if err != errLockViolation {
@@ -75,8 +86,11 @@ func flock(f *os.File, exclusive bool, timeout time.Duration) error {
 }
 
 // funlock releases an advisory lock on a file descriptor.
-func funlock(f *os.File) error {
-	return unlockFileEx(syscall.Handle(f.Fd()), 0, 1, 0, &syscall.Overlapped{})
+func funlock(db *DB) error {
+	err := unlockFileEx(syscall.Handle(db.lockfile.Fd()), 0, 1, 0, &syscall.Overlapped{})
+	db.lockfile.Close()
+	os.Remove(db.path + lockExt)
+	return err
 }
 
 // mmap memory maps a DB's data file.