How can I knit rmd with params and choose the multiple select input as input for group by?

I'm trying to create an rmd report with params.

---
...
output:
  html_document:
params:
  features:
    label: features
    value: ""
    input: select
    multiple: TRUE
    choices: [blue, red, green, yellow]
---

Then I want to use the features as grouping variables.

df %>%
  group_by(params$features) %>%
  summarize(x = sum(x))

But the but when I print them out

params$features

## [1] "blue" "red" "green" "yellow"

...

And this is the error code

Quitting from lines 65-74 (clustern.rmd) 
Error: Problem adding computed columns in `group_by()`.
x Problem with `mutate()` input `..1`.
ℹ `..1 = params$features`.
ℹ `..1` must be size 1163210 or 1, not 3.
...

I'm sure it's not that hard to solve but I searched succesless the web :/

I hope someone can solve this, thx!!

As these are character elements, an easier option is to use across within group_by

library(dplyr)
df %>% 
   group_by(across(all_of(params$features))) %>% 
   summarise(x = sum(x, na.rm = TRUE))