pm2 cluster mode can not assign different process.env to worker as nodejs cluster.fork([env]) does

What's going wrong?

pm2 cluster mode can not assign different process.env to worker as nodejs cluster.fork([env]) does.
For example, if not using pm2, my cluster.fork will assign different env for works, like following

if (cluster.isMaster) {
  x = [1, 2, 3, 4];
  for (let i = 0; i < 4; i++) {
    cluster.fork({x:x[i]}); //set different env for each worker
 }} else {
  console.log(process.env.x);
  //using its own process.env.x 
}

But it seems with pm2 I can't do that.

$ pm2 report

--- PM2 report ----------------------------------------------------------------
Date                 : Tue Aug 02 2022 14:22:38 GMT+0800 (China Standard Time)
===============================================================================
--- Daemon -------------------------------------------------
pm2d version         : 5.2.0
node version         : 16.14.2
node path            : /Users/qiulang/Projects/call-center/ws_redis/node_modules/.bin/pm2
argv                 : /usr/local/bin/node,/Users/qiulang/Projects/call-center/ws_redis/node_modules/pm2/lib/Daemon.js
argv0                : node
user                 : qiulang
uid                  : 501
gid                  : 20
uptime               : 922min
===============================================================================
--- CLI ----------------------------------------------------
local pm2            : 5.2.0
node version         : 16.14.2
node path            : /Users/qiulang/Projects/call-center/ws_redis/node_modules/.bin/pm2
argv                 : /usr/local/bin/node,/Users/qiulang/Projects/call-center/ws_redis/node_modules/.bin/pm2,report
argv0                : node
user                 : qiulang
uid                  : 501
gid                  : 20
===============================================================================
--- System info --------------------------------------------
arch                 : arm64
platform             : darwin
type                 : Darwin
cpus                 : Apple M1
cpus nb              : 8
freemem              : 139640832
totalmem             : 8589934592
home                 : /Users/qiulang
===============================================================================
--- PM2 list -----------------------------------------------
┌─────┬─────────────┬─────────────┬─────────┬─────────┬──────────┬────────┬──────┬───────────┬──────────┬──────────┬──────────┬──────────┐
│ id  │ name        │ namespace   │ version │ mode    │ pid      │ uptime │ ↺    │ status    │ cpu      │ mem      │ user     │ watching │
├─────┼─────────────┼─────────────┼─────────┼─────────┼──────────┼────────┼──────┼───────────┼──────────┼──────────┼──────────┼──────────┤
│ 0   │ ws_redis    │ default     │ 2.0.0   │ fork    │ 0        │ 0      │ 0    │ stopped   │ 0%       │ 0b       │ qiulang  │ disabled │
└─────┴─────────────┴─────────────┴─────────┴─────────┴──────────┴────────┴──────┴───────────┴──────────┴──────────┴──────────┴──────────┘
===============================================================================
--- Daemon logs --------------------------------------------
/Users/qiulang/.pm2/pm2.log last 20 lines:
PM2        | 2022-08-01T23:00:27: PM2 log: --- New PM2 Daemon started ----------------------------------------------------
PM2        | 2022-08-01T23:00:27: PM2 log: Time                 : Mon Aug 01 2022 23:00:27 GMT+0800 (China Standard Time)
PM2        | 2022-08-01T23:00:27: PM2 log: PM2 version          : 5.2.0
PM2        | 2022-08-01T23:00:27: PM2 log: Node.js version      : 16.14.2
PM2        | 2022-08-01T23:00:27: PM2 log: Current arch         : arm64
PM2        | 2022-08-01T23:00:27: PM2 log: PM2 home             : /Users/qiulang/.pm2
PM2        | 2022-08-01T23:00:27: PM2 log: PM2 PID file         : /Users/qiulang/.pm2/pm2.pid
PM2        | 2022-08-01T23:00:27: PM2 log: RPC socket file      : /Users/qiulang/.pm2/rpc.sock
PM2        | 2022-08-01T23:00:27: PM2 log: BUS socket file      : /Users/qiulang/.pm2/pub.sock
PM2        | 2022-08-01T23:00:27: PM2 log: Application log path : /Users/qiulang/.pm2/logs
PM2        | 2022-08-01T23:00:27: PM2 log: Worker Interval      : 30000
PM2        | 2022-08-01T23:00:27: PM2 log: Process dump file    : /Users/qiulang/.pm2/dump.pm2
PM2        | 2022-08-01T23:00:27: PM2 log: Concurrent actions   : 2
PM2        | 2022-08-01T23:00:27: PM2 log: SIGTERM timeout      : 1600
PM2        | 2022-08-01T23:00:27: PM2 log: ===============================================================================
PM2        | 2022-08-01T23:00:27: PM2 log: App [ws_redis:0] starting in -fork mode-
PM2        | 2022-08-01T23:00:27: PM2 log: App [ws_redis:0] online
PM2        | 2022-08-01T23:01:04: PM2 log: Stopping app:ws_redis id:0
PM2        | 2022-08-01T23:01:04: PM2 log: App [ws_redis:0] exited with code [0] via signal [SIGINT]
PM2        | 2022-08-01T23:01:04: PM2 log: pid=3982 msg=process killed

No repository file or test is named. Start by tracing PM2 cluster mode against Node.js cluster.fork([env]) and its per-worker environment handling; done means workers can receive distinct process.env values and a regression test covers the behavior.