internal/gocommand: show pid of process

We're almost certain that the go process shown by ps
is not the one that we're waiting for in runCmdContext,
but only by printing the pid can we be sure.

Updates golang/go#54461

Change-Id: I1ce9580de6ee6bc4557d76c2a6b05f5a3e2eb6c2
Reviewed-on: https://go-review.googlesource.com/c/tools/+/434637
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Alan Donovan <adonovan@google.com>
gopls-CI: kokoro <noreply+kokoro@google.com>
Reviewed-by: Robert Findley <rfindley@google.com>

internal/gocommand/invoke.go

@@ -258,7 +258,7 @@ func runCmdContext(ctx context.Context, cmd *exec.Cmd) error {
 		case err := <-resChan:
 			return err
 		case <-time.After(1 * time.Minute):
-			HandleHangingGoCommand()
+			HandleHangingGoCommand(cmd.Process)
 		case <-ctx.Done():
 		}
 	} else {
@@ -291,13 +291,13 @@ func runCmdContext(ctx context.Context, cmd *exec.Cmd) error {
 		case err := <-resChan:
 			return err
 		case <-time.After(10 * time.Second): // a shorter wait as resChan should return quickly following Kill
-			HandleHangingGoCommand()
+			HandleHangingGoCommand(cmd.Process)
 		}
 	}
 	return <-resChan
 }
 
-func HandleHangingGoCommand() {
+func HandleHangingGoCommand(proc *os.Process) {
 	switch runtime.GOOS {
 	case "linux", "darwin", "freebsd", "netbsd":
 		fmt.Fprintln(os.Stderr, `DETECTED A HANGING GO COMMAND
@@ -330,7 +330,7 @@ See golang/go#54461 for more details.`)
 			panic(fmt.Sprintf("running %s: %v", listFiles, err))
 		}
 	}
-	panic("detected hanging go command: see golang/go#54461 for more details")
+	panic(fmt.Sprintf("detected hanging go command (pid %d): see golang/go#54461 for more details", proc.Pid))
 }
 
 func cmdDebugStr(cmd *exec.Cmd) string {