improve inserting comments on new lines for go

Now it matches the behavior from c-family, python, and zig

Author: arrufat

rc/filetype/go.kak

@@ -132,12 +132,24 @@ define-command -hidden go-indent-on-closing-curly-brace %[
     try %[ execute-keys -itersel -draft <a-h><a-k>^\h+\}$<ret>hms\A|.\z<ret>1<a-&> ]
 ]
 
-define-command -hidden go-insert-comment-on-new-line %[
-    evaluate-commands -no-hooks -draft -itersel %[
-        # copy // comments prefix and following white spaces
-        try %{ execute-keys -draft <semicolon><c-s>kx s ^\h*\K/{2,}\h* <ret> y<c-o>P<esc> }
+define-command -hidden go-insert-comment-on-new-line %[ evaluate-commands -itersel -draft %[
+    execute-keys <semicolon>
+    try %[
+        evaluate-commands -draft -save-regs '/"' %[
+            # copy the commenting prefix
+            execute-keys -save-regs '' k x1s^\h*(//+\h*)<ret> y
+            try %[
+                # if the previous comment isn't empty, create a new one
+                execute-keys x<a-K>^\h*//+\h*$<ret> jxs^\h*<ret>P
+            ] catch %[
+                # if there is no text in the previous comment, remove it completely
+                execute-keys d
+            ]
+        ]
+        # trim trailing whitespace on the previous line
+        try %[ execute-keys -draft k x s\h+$<ret> d ]
     ]
-]
+] ]
 
 define-command -hidden go-insert-closing-delimiter-on-new-line %[
     evaluate-commands -no-hooks -draft -itersel %[