docs: mention go help testflags

README.md

@@ -358,8 +358,8 @@ configuring Go and the neotest-golang adapter in a separate file
 
 You can set the optional neotest-go `go_test_args` to control the number of test
 binaries and number of tests to run in parallel using the `-p` and `-parallel`
-flags, respectively. Execute `go help test` for more information on this and
-perhaps have a look at
+flags, respectively. Execute `go help test` and `go help testflag` for more
+information on this and perhaps have a look at
 [my own configuration](https://github.com/fredrikaverpil/dotfiles/blob/main/nvim-fredrik/lua/lang/go.lua)
 for inspiration.