Fix.

src/setup-ruby.ts

@@ -0,0 +1,13 @@
+import * as core from '@actions/core';
+import findRubyVersion from './installer';
+
+async function run() {
+  try {
+    const version = core.getInput('version');
+    await findRubyVersion(version);
+  } catch (error) {
+    core.setFailed(error.message);
+  }
+}
+
+run();