runtime: use slightly lower UDS path limit for mac reasons

The max length of a unix domain socket path is slightly lower on mac than it is
on linux, and it keeps causing me issues during testing.  If a path ended up
being between 105-107 characters long, it would not get hashed (shortened) on
mac, which causes the runtime to fail.  This tweaks our existing hacky
workaround to make things more reliable on mac, without significantly changing
the behavior on linux.  This is sort of like adding duct tape over top of
chewing gum, I know, but it makes local testing on mac far less frustrating.

Author: psFried

go/bindings/task_service.go

@@ -81,11 +81,14 @@ func NewTaskService(
 		}
 	}
 
-	// Unix sockets are limited to 108 characters in length.
+	// Unix sockets are limited to 104 characters in length on mac. Linux allows 107, but we
+	// respect the slightly lower limit here instead of having separate limits per OS.
 	// TODO(johnny): Remove hashing after pet-set migration, when we know there's a bound on directory length.
-	if len(config.UdsPath) > 107 {
+	if len(config.UdsPath) > 104 {
 		config.UdsPath = path.Join(os.TempDir(), fmt.Sprintf("task-svc-%x", md5.Sum([]byte(config.UdsPath))))
-
+		// 107 is intentional here. If we're on mac and the path is still longer than 104, we'll still raise
+		// an error from the rust runtime. But we tend to have paths that are still very close to the limit,
+		// so this ensures that we don't return errors unnecessarily on linux.
 		if len(config.UdsPath) > 107 {
 			return nil, fmt.Errorf("config.UdsPath still too long after hashing: %s", config.UdsPath)
 		}