R plumber with future promise: assign variable to global environment

Question

In a R plumber script in which I use future I need to assign some variables to the global environment (so that a variable created in one API can be retrieved from another API) but it does not work as expected.

I created a simple example. Here you can see the main script to run in R:

### Set the asynchronous coding
library(promises) ; library(future)
future::plan("multisession")

## Plumber app
library(plumber)

pr <- pr("APIs_TestAsync.R")
pr %>% pr_run()

and here the script to save as "APIs_TestAsync.R":

#* Test 1
#* @get test1
#* @serializer unboxedJSON
#* @tag TestFuture
function() {
  
  # Create a dataset
  df<-data.frame(A=c("a", "a", "a", "b", "b", "c"), B=c(1,2,3,4,5,6))
  assign("Test1", df, .GlobalEnv)

  return(
    list(SUM=sum(df$B))
    )
  }


#* Test 2
#* @get test2
#* @serializer unboxedJSON
#* @tag TestFuture
function() {
  
  # Create a future promise
  Prom<-future({
    
      # Wait for 10 seconds (needed to test the asynchronous functions)
      Sys.sleep(10)
  
      # Create a dataset
      df<-data.frame(A=c("a", "a", "a", "b", "b", "c"), B=c(1,2,3,4,5,6))
      assign("Test2", df, .GlobalEnv)

      # Store the list in Prom
      return(
        list(SUM=sum(df$B))
      )

  }, seed=T) # Close future promise
  
  return(Prom) # Return Prom to the API

}

You'll see that the first API (not using future) manages to assign Test1 to the global environment but that the second API does not assign Test2.

I tried several ways of assignment, different environment names, explored the futureAssign function but did not manage to make it work...

If you have any idea it would be greatly appreciated!