callr: callr futures
In future.callr: A Future API for Parallel Processing using 'callr'

A callr future is an asynchronous multiprocess future that will be evaluated in a background R session.

callr(
  expr,
  envir = parent.frame(),
  substitute = TRUE,
  globals = TRUE,
  label = NULL,
  workers = availableCores(),
  ...
)

`expr`	The R expression to be evaluated.
`envir`	The environment in which global environment should be located.
`substitute`	Controls whether `expr` should be `substitute()`:d or not.
`globals`	(optional) a logical, a character vector, a named list, or a globals::Globals object. If `TRUE`, globals are identified by code inspection based on `expr` and `tweak` searching from environment `envir`. If `FALSE`, no globals are used. If a character vector, then globals are identified by lookup based their names `globals` searching from environment `envir`. If a named list or a Globals object, the globals are used as is.
`label`	(optional) Label of the future.
`workers`	The number of processes to be available for concurrent callr futures.
`...`	Additional arguments passed to `CallrFuture()`.