Add explicit process.exit() to avoid wait for hanging promises

When using the `@actions/cache` library to save cache entries, it seems that one
or more Promises remain unresolved after the save completes.
With Node20 this causes a delay when exiting the process: the default behaviour
now wait for these Promises to complete. Adding an explicit `Process.exit()`
removes the delay, returning to the Node 16 behaviour.

Fixes #1038

dist/main/index.js

@@ -140762,10 +140762,10 @@ function run() {
                 core.info(error.stack);
             }
         }
+        process.exit();
     });
 }
 exports.run = run;
-run();
 
 
 /***/ }),

dist/post/index.js

@@ -138072,10 +138072,12 @@ function run() {
         catch (error) {
             if (error instanceof errors_1.PostActionJobFailure) {
                 core.setFailed(String(error));
-                return;
             }
-            handleFailure(error);
+            else {
+                handleFailure(error);
+            }
         }
+        process.exit();
     });
 }
 exports.run = run;
@@ -138085,7 +138087,6 @@ function handleFailure(error) {
         core.info(error.stack);
     }
 }
-run();
 
 
 /***/ }),

src/main.ts

@@ -29,6 +29,7 @@ export async function run(): Promise<void> {
             core.info(error.stack)
         }
     }
-}
 
-run()
+    // Explicit process.exit() to prevent waiting for hanging promises.
+    process.exit()
+}

src/post.ts

@@ -16,11 +16,13 @@ export async function run(): Promise<void> {
     } catch (error) {
         if (error instanceof PostActionJobFailure) {
             core.setFailed(String(error))
-            return
+        } else {
+            handleFailure(error)
         }
-
-        handleFailure(error)
     }
+
+    // Explicit process.exit() to prevent waiting for promises left hanging by `@actions/cache` on save.
+    process.exit()
 }
 
 function handleFailure(error: unknown): void {
@@ -29,5 +31,3 @@ function handleFailure(error: unknown): void {
         core.info(error.stack)
     }
 }
-
-run()