Update default Go module caching to use go.mod (#705)

* Update module cache to use go.mod as key

* Fix typo

* Revise breaking changes in README for V6

Updated breaking changes section with enhanced formatting and clarified toolchain management details.

src/cache-restore.ts

@@ -55,8 +55,8 @@ const findDependencyFile = (packageManager: PackageManagerInfo) => {
   const workspace = process.env.GITHUB_WORKSPACE!;
   const rootContent = fs.readdirSync(workspace);
 
-  const goSumFileExists = rootContent.includes(dependencyFile);
-  if (!goSumFileExists) {
+  const goModFileExists = rootContent.includes(dependencyFile);
+  if (!goModFileExists) {
     throw new Error(
       `Dependencies file is not found in ${workspace}. Supported file pattern: ${dependencyFile}`
     );

src/package-managers.ts

@@ -9,7 +9,7 @@ export interface PackageManagerInfo {
 
 export const supportedPackageManagers: SupportedPackageManagers = {
   default: {
-    dependencyFilePattern: 'go.sum',
+    dependencyFilePattern: 'go.mod',
     cacheFolderCommandList: ['go env GOMODCACHE', 'go env GOCACHE']
   }
 };