Set lsp-prefer-flymake to :none when Go layer is using LSP

When switching the Go layer to use the LSP backend with `golangci-lint`, I
noticed that none of my linter errors were being rendered with my source code.
Digging in further, I eventually learned it was due to `lsp-prefer-flymake`
being set to `nil` and not `:none`.

This change updates the Go layer, when using LSP and golangci-lint, to set
`lsp-prefer-flymake` to `:none`. If this is not set, the golangci-lint errors
will not be reported.

This is an alternative to #12043.

Fixes #11680

Signed-off-by: Tim Heckman <t@heckman.io>

CHANGELOG.develop

@@ -1300,6 +1300,8 @@ Other:
 - Added lsp support (thanks to Lupco Kotev)
 - Added golangci-lint support (thanks to Lupco Kotev)
 - Add toggle control for verbose go test output (thanks to Enze Chi)
+- Set lsp-prefer-flymake to :none when Go layer is using LSP (thanks to Tim
+  Heckman)
 **** Graphviz
 - Use graphviz package from melpa (thanks to Matthew Boston)
 **** Groovy

layers/+lang/go/funcs.el

@@ -37,7 +37,13 @@
 (defun spacemacs//go-setup-backend-lsp ()
   "Setup lsp backend"
   (if (configuration-layer/layer-used-p 'lsp)
-      (lsp)
+      (progn
+        ;; without setting lsp-prefer-flymake to :none
+        ;; golangci-lint errors won't be reported
+        (when go-use-golangci-lint
+          (message "[go] Setting lsp-prefer-flymake :none to enable golangci-lint support.")
+          (setq-local lsp-prefer-flymake :none))
+        (lsp))
     (message "`lsp' layer is not installed, please add `lsp' layer to your dotfile.")))
 
 (defun spacemacs//go-setup-company-lsp ()