Create ADR for integrating cache functionality to setup-go action (ac…

…tions#217)

docs/adrs/0000-caching-dependencies.md

@@ -0,0 +1,69 @@
+# 0. Caching dependencies
+Date: 2022-04-13
+
+Status: Accepted
+
+# Context
+`actions/setup-go` is the one of the most popular action related to Golang in GitHub Actions. Many customers use it in conjunction with [actions/cache](https://github.com/actions/cache) to speed up dependency installation process.  
+See more examples on proper usage in [actions/cache documentation](https://github.com/actions/cache/blob/main/examples.md#go---modules).
+
+# Goals & Anti-Goals
+Integration of caching functionality into `actions/setup-go` action will bring the following benefits for action users:
+- Decrease the entry threshold for using the cache for Go dependencies and simplify initial configuration
+- Simplify YAML pipelines because there will be no need for additional steps to enable caching
+- More users will use cache for Go so more customers will have fast builds!
+
+We don't pursue the goal to provide wide customization of caching in scope of `actions/setup-go` action. The purpose of this integration is covering ~90% of basic use-cases. If user needs flexible customization, we should advice them to use `actions/cache` directly.
+
+# Decision
+- Add `cache` input parameter to `actions/setup-go`. For now, input will accept the following values: 
+  - `true` - enable caching for go dependencies
+  - `false`- disable caching for go dependencies. This value will be set as default value
+- Cache feature will be disabled by default to make sure that we don't break existing customers. We will consider enabling cache by default in next major releases
+- Action will try to search a go.sum files in the repository and throw error in the scenario that it was not found
+- The hash of found file will be used as cache key (the same approach like [actions/cache](https://github.com/actions/cache/blob/main/examples.md#go---modules) recommends)
+- The following key cache will be used `${{ runner.os }}-go${{ go-version }}-${{ hashFiles('<go.sum-path>') }}`
+- Action will cache global cache from the `go env GOMODCACHE` and `go env GOCACHE` commands.
+- Add a `cache-dependency-path` input parameter to `actions/setup-go`. The new input will accept an array or regex of dependency files. The field will accept a path (relative to the repository root) to dependency files. If the provided path contains wildcards, the action will search all matching files and calculate a common hash like the ${{ hashFiles('**/go.sum') }} YAML construction does.
+
+# Example of real use-cases
+
+ - With cache
+
+```yml
+steps:
+- uses: actions/checkout@v3
+- uses: actions/setup-go@v3
+  with:
+    go-version: '18'
+    cache: true
+```
+
+ - With cache-dependency-path
+
+ ```yml
+steps:
+- uses: actions/checkout@v3
+- uses: actions/setup-go@v3
+  with:
+    go-version: '18'
+    cache: true
+    cache-dependency-path: **/go.sum
+```
+
+ ```yml
+steps:
+- uses: actions/checkout@v3
+- uses: actions/setup-go@v3
+  with:
+    go-version: '18'
+    cache: true
+    cache-dependency-path: |
+        **/go.sum
+        **/go.mod
+```
+
+# Release process
+
+As soon as functionality is implemented, we will release minor update of action. No need to bump major version since there are no breaking changes for existing users.
+After that, we will update [starter-workflows](https://github.com/actions/starter-workflows/blob/main/ci/go.yml)