fix: load piscina only if available

Signed-off-by: Tuan Anh Tran <me@tuananh.org>

.github/workflows/ci.yaml

@@ -9,7 +9,7 @@ jobs:
             fail-fast: false
             matrix:
                 os: [ubuntu-latest, macos-latest, windows-latest]
-                node-version: [12.x, 13.x, 14.x, 15.x]
+                node-version: [10.x, 11.x, 12.x, 13.x, 14.x, 15.x]
         runs-on: ${{matrix.os}}
         steps:
             - uses: actions/checkout@v2

index.js

@@ -1,7 +1,19 @@
 const { resolve } = require('path')
-const WorkerPool = require('piscina')
 
-const pool = new WorkerPool({ filename: resolve(__dirname, 'worker.js') })
+let pool = null
+try {
+    const WorkerPool = require('piscina')
+    pool = new WorkerPool({ filename: resolve(__dirname, 'worker.js') })
+} catch(e) {
+    if (e.code === 'MODULE_NOT_FOUND') {
+        console.warn('[camaro] worker_threads is not available, expect performance drop. Try using Node version >= 12.')
+    }
+
+    const workerFn = require('./worker')
+    pool = {
+        runTask: async (args) => workerFn(args)
+    }
+}
 
 function isNonEmptyString(str) {
     return typeof str === 'string' && str.length > 0