doc: update the instruction to use beta2

And include the link to the milestone and a known issue

Change-Id: Iaae07cdf1a533da44fd15e0692b29e4173ed879f
Reviewed-on: https://go-review.googlesource.com/c/tools/+/381016
Trust: Hyang-Ah Hana Kim <hyangah@gmail.com>
Run-TryBot: Hyang-Ah Hana Kim <hyangah@gmail.com>
Reviewed-by: Robert Findley <rfindley@google.com>
gopls-CI: kokoro <noreply+kokoro@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>

gopls/doc/advanced.md

@@ -50,26 +50,38 @@ Gopls has beta support for editing generic Go code, as defined by the type
 parameters proposal ([golang/go#43651](https://golang.org/issues/43651)) and
 type set addendum ([golang/go#45346](https://golang.org/issues/45346)).
 
-To enable this support, you need to build gopls with a version of Go that
-supports generics. The easiest way to do this is by installing Go 1.18 Beta
-1 as described at
+To enable this support, you need to **build gopls with a version of Go that
+supports generics**. The easiest way to do this is by installing the Go 1.18 Beta
+as described at
 [Tutorial: Getting started with generics#prerequisites](https://go.dev/doc/tutorial/generics),
 and then using this Go version to build gopls:
 
 ```
-$ go1.18beta1 install golang.org/x/tools/gopls@latest
+$ go1.18beta2 install golang.org/x/tools/gopls@latest
 ```
 
 When using the Go 1.18, it is strongly recommended that you install the latest
 version of `gopls`, or the latest **unstable** version as
 [described above](#installing-unreleased-versions).
 
+You also need to make `gopls` select the beta version of `go` (in `<GOROOT>/go/bin`
+where GOROOT is the location reported by `go1.18beta2 env GOROOT`) by adding
+it to your `PATH` or by configuring your editor.
+
 The `gopls` built with these instructions understands generic code. To actually
 run the generic code you develop, you must also use the beta version of the Go
 compiler. For example:
 
 ```
-$ go1.18beta1 run .
+$ go1.18beta2 run .
 ```
 
+### Known issues
+
+  * [`staticcheck`](https://github.com/golang/tools/blob/master/gopls/doc/settings.md#staticcheck-bool)
+    on generic code is not supported yet.
+
+please follow the [v0.8.0](https://github.com/golang/go/milestone/244) milestone
+to see the list of go1.18-related known issues and our progress.
+
 [Go project]: https://go.googlesource.com/go