lockedfile: update to Go tip as of March 2023

As of commit 7a21f799a5ac23d3e191a106d71af9b8f65279fd,
which is crucially right before https://go.dev/cl/476917,
as then internal/filelock starts using Go 1.21's errors.ErrUnsupported.
We still want to support Go 1.19 and 1.20 for a while.

The only change besides the import path rewriting is to drop testenv,
which was only used for MustHaveExec and Command.

Note that we no longer need to worry about unix build tags,
as we now require Go 1.19 or later.

lockedfile/internal/filelock/filelock_fcntl.go

@@ -3,7 +3,6 @@
 // license that can be found in the LICENSE file.
 
 //go:build aix || (solaris && !illumos)
-// +build aix solaris,!illumos
 
 // This code implements the filelock API using POSIX 'fcntl' locks, which attach
 // to an (inode, process) pair rather than a file descriptor. To avoid unlocking

lockedfile/internal/filelock/filelock_other.go

@@ -2,8 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//go:build !aix && !darwin && !dragonfly && !freebsd && !linux && !netbsd && !openbsd && !plan9 && !solaris && !windows
-// +build !aix,!darwin,!dragonfly,!freebsd,!linux,!netbsd,!openbsd,!plan9,!solaris,!windows
+//go:build !unix && !windows
 
 package filelock
 

lockedfile/internal/filelock/filelock_test.go

@@ -3,7 +3,6 @@
 // license that can be found in the LICENSE file.
 
 //go:build !js && !plan9
-// +build !js,!plan9
 
 package filelock_test
 

lockedfile/internal/filelock/filelock_unix.go

@@ -3,7 +3,6 @@
 // license that can be found in the LICENSE file.
 
 //go:build darwin || dragonfly || freebsd || illumos || linux || netbsd || openbsd
-// +build darwin dragonfly freebsd illumos linux netbsd openbsd
 
 package filelock
 

lockedfile/internal/filelock/filelock_windows.go

@@ -3,7 +3,6 @@
 // license that can be found in the LICENSE file.
 
 //go:build windows
-// +build windows
 
 package filelock
 

lockedfile/lockedfile_test.go

@@ -43,19 +43,32 @@ func mustBlock(t *testing.T, desc string, f func()) (wait func(*testing.T)) {
 		close(done)
 	}()
 
+	timer := time.NewTimer(quiescent)
+	defer timer.Stop()
 	select {
 	case <-done:
 		t.Fatalf("%s unexpectedly did not block", desc)
-		return nil
+	case <-timer.C:
+	}
+
+	return func(t *testing.T) {
+		logTimer := time.NewTimer(quiescent)
+		defer logTimer.Stop()
 
-	case <-time.After(quiescent):
-		return func(t *testing.T) {
+		select {
+		case <-logTimer.C:
+			// We expect the operation to have unblocked by now,
+			// but maybe it's just slow. Write to the test log
+			// in case the test times out, but don't fail it.
 			t.Helper()
-			select {
-			case <-time.After(probablyStillBlocked):
-				t.Fatalf("%s is unexpectedly still blocked after %v", desc, probablyStillBlocked)
-			case <-done:
-			}
+			t.Logf("%s is unexpectedly still blocked after %v", desc, quiescent)
+
+			// Wait for the operation to actually complete, no matter how long it
+			// takes. If the test has deadlocked, this will cause the test to time out
+			// and dump goroutines.
+			<-done
+
+		case <-done:
 		}
 	}
 }
@@ -242,10 +255,12 @@ locked:
 		if _, err := os.Stat(filepath.Join(dir, "locked")); !os.IsNotExist(err) {
 			break locked
 		}
+		timer := time.NewTimer(1 * time.Millisecond)
 		select {
 		case <-qDone:
+			timer.Stop()
 			break locked
-		case <-time.After(1 * time.Millisecond):
+		case <-timer.C:
 		}
 	}