I have a multi-select html form element which allows a user to select multiple categories. On form validation error, I would like to be able to reselect the categories the user had already selected.

Issues:

First, when calling FlashParams() with a slice parameter, the key becomes "slice[]", but when attempting to access the flash variable in a template via {{.slice[]}} results in "bad character U+005B '['"

Second, only the first value in the slice is set in the flash cookie. There is the limitation of flash being a string map, so the multiple values would have to be represented as a string. I was thinking you could escape backslashes and commas and use a comma separated list. This could be made into is own function that FlashParams() can call or can call when manually setting flash data. A template function would then be required to iterate over the comma separated list.

I think its a problem worth solving sooner or later. Any feedback would be appreciated.