feat: use OS and working-directory as cache key (#1032)

Author: ldez

Diff for: README.md

@@ -308,10 +308,11 @@ Inside our action, we perform 3 steps:
 ### Caching internals
 
 1. We save and restore the following directory: `~/.cache/golangci-lint`.
-2. The primary caching key looks like `golangci-lint.cache-{interval_number}-{go.mod_hash}`.
+2. The primary caching key looks like `golangci-lint.cache-{runner_os}-{working_directory}-{interval_number}-{go.mod_hash}`.
    Interval number ensures that we periodically invalidate our cache (every 7 days).
    `go.mod` hash ensures that we invalidate the cache early - as soon as dependencies have changed.
-3. We use [restore keys](https://help.github.com/en/actions/configuring-and-managing-workflows/caching-dependencies-to-speed-up-workflows#matching-a-cache-key): `golangci-lint.cache-{interval_number}-`. 
+3. We use [restore keys](https://help.github.com/en/actions/configuring-and-managing-workflows/caching-dependencies-to-speed-up-workflows#matching-a-cache-key):
+   `golangci-lint.cache-{runner_os}-{working_directory}-{interval_number}-`.
    GitHub matches keys by prefix if we have no exact match for the primary cache.
 
 This scheme is basic and needs improvements. Pull requests and ideas are welcome.

Diff for: dist/post_run/index.js

@@ -38,15 +38,22 @@ const getIntervalKey = (invalidationIntervalDays: number): string => {
 async function buildCacheKeys(): Promise<string[]> {
   const keys = []
 
-  const invalidationIntervalDays = parseInt(core.getInput(`cache-invalidation-interval`, { required: true }).trim())
-
-  // Periodically invalidate a cache because a new code being added.
-  let cacheKey = `golangci-lint.cache-${getIntervalKey(invalidationIntervalDays)}-`
-  keys.push(cacheKey)
+  // Cache by OS.
+  let cacheKey = `golangci-lint.cache-${process.env?.RUNNER_OS}-`
 
   // Get working directory from input
   const workingDirectory = core.getInput(`working-directory`)
 
+  if (workingDirectory) {
+    cacheKey += `${workingDirectory}-`
+  }
+
+  // Periodically invalidate a cache because a new code being added.
+  const invalidationIntervalDays = parseInt(core.getInput(`cache-invalidation-interval`, { required: true }).trim())
+  cacheKey += `${getIntervalKey(invalidationIntervalDays)}-`
+
+  keys.push(cacheKey)
+
   // create path to go.mod prepending the workingDirectory if it exists
   const goModPath = path.join(workingDirectory, `go.mod`)