Enable extra flags in 'go-ts-mode' test commands

* lisp/progmodes/go-ts-mode.el (go-ts-mode-test-flags):
(go-ts-mode--get-test-flags): New custom variable and function
for controlling test behaviour.
(go-ts-mode--compile-test): Updated to use new test flags
variable for passing extra information to the go test command
line.
(go-ts-mode-test-this-package): Updated to use new test flags
variable for passing extra information to the go test command
line.  Removed incorrect use of -run flag.

* etc/NEWS: Announce the new user option.  (Bug#74786)

etc/NEWS

@@ -548,6 +548,10 @@ package of the current buffer.  It is bound to 'C-c C-t p' in 'go-ts-mode'.
 The 'go-ts-mode-build-tags' user option is available to set a list of
 build tags for the test commands.
 
+The 'go-ts-mode-test-flags' user option is available to set a list of
+additional flags to pass to the go test command line.
+
+
 ** C-ts mode
 
 +++

lisp/progmodes/go-ts-mode.el

@@ -53,6 +53,12 @@
   :type '(repeat string)
   :group 'go)
 
+(defcustom go-ts-mode-test-flags nil
+  "List of extra flags for the Go test commands."
+  :version "31.1"
+  :type '(repeat string)
+  :group 'go)
+
 (defvar go-ts-mode--syntax-table
   (let ((table (make-syntax-table)))
     (modify-syntax-entry ?+   "."      table)
@@ -393,13 +399,20 @@ specifying build tags."
       (format "-tags %s" (string-join go-ts-mode-build-tags ","))
     ""))
 
+(defun go-ts-mode--get-test-flags ()
+  "Return the flags for test invocation."
+  (if go-ts-mode-test-flags
+      (mapconcat #'shell-quote-argument go-ts-mode-test-flags " ")
+    ""))
+
 (defun go-ts-mode--compile-test (regexp)
   "Compile the tests matching REGEXP.
 This function respects the `go-ts-mode-build-tags' variable for
 specifying build tags."
-  (compile (format "go test -v %s -run '%s'"
+  (compile (format "go test -v %s -run '%s' %s"
                    (go-ts-mode--get-build-tags-flag)
-                   regexp)))
+                   regexp
+                   (go-ts-mode--get-test-flags))))
 
 (defun go-ts-mode--find-defun-at (start)
   "Return the first defun node from START."
@@ -458,9 +471,10 @@ be run."
 (defun go-ts-mode-test-this-package ()
   "Run all the unit tests under the current package."
   (interactive)
-  (compile (format "go test -v %s -run %s"
+  (compile (format "go test -v %s %s %s"
                    (go-ts-mode--get-build-tags-flag)
-                   default-directory)))
+                   default-directory
+                   (go-ts-mode--get-test-flags))))
 
 ;; go.mod support.