README.md: clarify supported go & tools versions

Based on the clarified version support policy:

- Add github.com/golang/vscode-go/wiki/compatibility
to have the version compatibility matrix.

- Drop go1.20 from GH action workflows.

- Let extension/tools/installtools require go1.21+.

For #3411
For #3412

Change-Id: I10ffafa3234e691e9e27f84385aa68efa7db733f
Reviewed-on: https://go-review.googlesource.com/c/vscode-go/+/616675
kokoro-CI: kokoro <noreply+kokoro@google.com>
Reviewed-by: Robert Findley <rfindley@google.com>
Commit-Queue: Hyang-Ah Hana Kim <hyangah@gmail.com>

Author: hyangah

.github/workflows/test-long-all.yml

@@ -17,7 +17,7 @@ jobs:
       matrix:
         os: [ubuntu-latest, windows-latest, macos-latest]
         version: ['stable', 'insiders']
-        go: ['1.20', '1.21', '1.22', '1.23']
+        go: ['1.21', '1.22', '1.23']
 
     steps:
       - name: Clone repository

.github/workflows/test-long.yml

@@ -16,7 +16,7 @@ jobs:
       matrix:
         os: [ubuntu-latest, windows-latest] # TODO: reenable macos-latest
         version: ['stable']
-        go: ['1.20', '1.21', '1.22', '1.23']
+        go: ['1.21', '1.22', '1.23']
 
     steps:
       - name: Clone repository

README.md

@@ -11,15 +11,15 @@ provides rich language support for the
 ## Requirements
 
 * Visual Studio Code 1.75 or newer (or editors compatible with VS Code 1.75+ APIs)
-* Go 1.19 or newer.
+* Go 1.21 or newer.
 
 ## Quick Start
 
 Welcome! 👋🏻<br/>
 Whether you are new to Go or an experienced Go developer, we hope this
 extension fits your needs and enhances your development experience.
 
-1.  Install [Go](https://go.dev) 1.19 or newer if you haven't already.
+1.  Install [Go](https://go.dev) 1.21 or newer if you haven't already.
 
 1.  Install the [VS Code Go extension].
 
@@ -182,6 +182,30 @@ post series](https://research.swtch.com/telemetry-uses) contains many more.
 Go telemetry is designed to be transparent and privacy-preserving. Learn more at
 [https://go.dev/doc/telemetry](https://go.dev/doc/telemetry).
 
+## Support Policy
+
+The Go extension is maintained by engineers on the
+[Go tools team](https://github.com/orgs/golang/teams/tools-team/members),
+who actively monitor the [VS Code Go](https://github.com/golang/vscode-go/issues)
+and the [Go](https://github.com/golang/go/issues?q=is%3Aissue+is%3Aopen+label%3Agopls)
+issue trackers.
+
+We support only the latest stable and pre-release versions of the extension.
+
+### Supported Go and tools
+
+The Go extension follows the [Go Release Policy](https://go.dev/doc/devel/release.html#policy),
+meaning that it _officially_ supports the two most recent major Go releases.
+The Go team maintains _best-effort_ support for the last three major Go versions.
+
+The Go extension relies on [tools](https://github.com/golang/vscode-go/wiki/tools)
+like `gopls` and `dlv` for its core functionalities and they have their own release
+policy and schedule. We test only against the latest versions of these tools.
+
+In case you need to work with an older version of Go, please check
+the [Compatibility] page and manually install the compatible version of
+the extension and tools.
+
 ## Contributing
 
 We welcome your contributions and thank you for working to improve the Go
@@ -211,11 +235,12 @@ conduct-related issue, please mail conduct@golang.org.
 [IntelliSense]: https://github.com/golang/vscode-go/wiki/features#intellisense
 [Code navigation]: https://github.com/golang/vscode-go/wiki/features#code-navigation
 [Code editing]: https://github.com/golang/vscode-go/wiki/features#code-editing
+[Compatibility]: https://github.com/golang/vscode-go/wiki/compatibility
 [diagnostics]: https://github.com/golang/vscode-go/wiki/features#diagnostics
 [testing]: https://github.com/golang/vscode-go/wiki/features#run-and-test-in-the-editor
 [debugging]: https://github.com/golang/vscode-go/wiki/debugging#features
 [full feature breakdown]: https://github.com/golang/vscode-go/wiki/features
 [workspace documentation]: https://github.com/golang/tools/blob/master/gopls/doc/workspace.md
 [`Go: Install/Update Tools` command]: https://github.com/golang/vscode-go/wiki/commands#go-installupdate-tools
 [Supported workspace layouts documentation]: https://github.com/golang/tools/blob/master/gopls/doc/workspace.md
-[Workspace Folders]: https://code.visualstudio.com/docs/editor/multi-root-workspaces
+[Workspace Folders]: https://code.visualstudio.com/docs/editor/multi-root-workspaces

docs/compatibility.md

@@ -0,0 +1,18 @@
+
+## Version Compatibility
+
+The table below lists the *last* version of the extension
+known to be compatible with old versions of Go, and the last versionof tools
+compatible with it.
+
+| Go version | Extension version | VS Code | Gopls     | Delve        |
+| ---------- | ----------------- | ------- | --------- | ------------ |
+| go1.20     | v0.42.1           | 1.75+   | v0.15.3   | v1.22.1      |
+| go1.19     | v0.42.1           | 1.75+   | v0.15.3   | v1.21.2      |
+| go1.18     | v0.41.3           | 1.75+   | v0.14.2   | v1.20.0      |
+| go1.17     | v0.39.1           | 1.67+   | v0.11.0   | v1.9.1       |
+| go1.16     | v0.39.1           | 1.67+   | v0.11.0   | v1.8.3       |
+
+### References
+  * Gopls's [supported go versions](https://github.com/golang/tools/tree/master/gopls#supported-go-versions).
+  * Delve's [supported go versions](https://github.com/go-delve/delve/blob/master/pkg/goversion/compat.go).

extension/tools/installtools/main.go

@@ -38,8 +38,8 @@ var tools = []struct {
 	{"golang.org/x/tools/gopls", "", true, nil},
 	{"github.com/cweill/gotests/gotests", "", false, nil},
 	{"github.com/haya14busa/goplay/cmd/goplay", "", false, nil},
-	{"honnef.co/go/tools/cmd/staticcheck", "", false, []finalVersion{{18, "v0.3.3"}, {20, "v0.4.7"}}},
-	{"github.com/go-delve/delve/cmd/dlv", "", false, []finalVersion{{16, "v1.8.3"}, {17, "v1.9.1"}, {18, "v1.20.2"}, {20, "v1.22.1"}}},
+	{"honnef.co/go/tools/cmd/staticcheck", "", false, []finalVersion{{21, "v0.4.7"}}},
+	{"github.com/go-delve/delve/cmd/dlv", "", false, nil},
 }
 
 // pickVersion returns the version to install based on the supported
@@ -58,7 +58,7 @@ func main() {
 	if err != nil {
 		exitf("failed to find go version: %v", err)
 	}
-	if ver < 1 {
+	if ver < 21 {
 		exitf("unsupported go version: 1.%v", ver)
 	}