diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index cde3a21..019f995 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -6,6 +6,10 @@ on:
   pull_request:
   workflow_dispatch:
 
+concurrency: # Cancel stale PR builds (but not push builds)
+  group: ${{ github.workflow }}-${{ github.event.pull_request.number || github.sha }}
+  cancel-in-progress: true
+
 jobs:
   build:
     strategy:
@@ -46,7 +50,7 @@ jobs:
     continue-on-error: ${{ matrix.branch == 'devel' }}
     steps:
       - name: Checkout
-        uses: actions/checkout@v2
+        uses: actions/checkout@v3
 
       - name: Install build dependencies (Linux i386)
         if: runner.os == 'Linux' && matrix.target.cpu == 'i386'
@@ -68,13 +72,6 @@ jobs:
           chmod 755 external/bin/gcc external/bin/g++
           echo '${{ github.workspace }}/external/bin' >> $GITHUB_PATH
 
-      - name: 'Install dependencies (macOS)'
-        if: runner.os == 'macOS' && matrix.branch == 'devel'
-        run: |
-          brew install openssl@1.1
-          ln -s $(brew --prefix)/opt/openssl/lib/libcrypto.1.1.dylib /usr/local/lib
-          ln -s $(brew --prefix)/opt/openssl/lib/libssl.1.1.dylib /usr/local/lib/
-
       - name: MSYS2 (Windows i386)
         if: runner.os == 'Windows' && matrix.target.cpu == 'i386'
         uses: msys2/setup-msys2@v2
@@ -117,7 +114,7 @@ jobs:
         if: >
           runner.os == 'Windows'
         run: |
-          echo '${{ github.workspace }}'"/external/dlls-${{ matrix.target.cpu }}" >> $GITHUB_PATH
+          echo "${{ github.workspace }}/external/dlls-${{ matrix.target.cpu }}" >> $GITHUB_PATH
 
       - name: Derive environment variables
         run: |
diff --git a/.gitignore b/.gitignore
index f2e7e9b..db41c85 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,4 +1,5 @@
-nimcache
+nimcache/
 *.exe
 nimble.develop
 nimble.paths
+/build/
diff --git a/chronos.nimble b/chronos.nimble
index 7362438..639d1d3 100644
--- a/chronos.nimble
+++ b/chronos.nimble
@@ -1,45 +1,47 @@
+mode = ScriptMode.Verbose
+
 packageName   = "chronos"
 version       = "3.0.11"
 author        = "Status Research & Development GmbH"
-description   = "Chronos"
-license       = "Apache License 2.0 or MIT"
+description   = "Networking framework with async/await support"
+license       = "MIT or Apache License 2.0"
 skipDirs      = @["tests"]
 
-### Dependencies
-
-requires "nim > 1.2.0",
+requires "nim >= 1.2.0",
          "stew",
          "bearssl",
          "httputils",
          "unittest2"
 
-var commandStart = "nim c -r --hints:off --verbosity:0 --skipParentCfg:on --warning[ObservableStores]:off --styleCheck:usages --styleCheck:error"
+let nimc = getEnv("NIMC", "nim") # Which nim compiler to use
+let lang = getEnv("NIMLANG", "c") # Which backend (c/cpp/js)
+let flags = getEnv("NIMFLAGS", "") # Extra flags for the compiler
+let verbose = getEnv("V", "") notin ["", "0"]
+
+let styleCheckStyle = if (NimMajor, NimMinor) < (1, 6): "hint" else: "error"
+let cfg =
+  " --styleCheck:usages --styleCheck:" & styleCheckStyle &
+  (if verbose: "" else: " --verbosity:0 --hints:off") &
+  " --skipParentCfg --skipUserCfg --outdir:build --nimcache:build/nimcache -f"
+
+proc build(args, path: string) =
+  exec nimc & " " & lang & " " & cfg & " " & flags & " " & args & " " & path
+
+proc run(args, path: string) =
+  build args & " -r", path
 
 task test, "Run all tests":
-  var commands = @[
-      commandStart & " -d:useSysAssert -d:useGcAssert tests/",
-      commandStart & " -d:chronosStackTrace -d:chronosStrictException tests/",
-      commandStart & " -d:release tests/",
-      commandStart & " -d:release -d:chronosFutureTracking tests/",
-    ]
-  when (NimMajor, NimMinor) >= (1, 5):
-    commands.add commandStart & " --gc:orc -d:chronosFutureTracking -d:release -d:chronosStackTrace tests/"
-
-  for testname in ["testall"]:
-    for cmd in commands:
-      let curcmd = cmd & testname
-      echo "\n" & curcmd
-      exec curcmd
-      rmFile "tests/" & testname
+  for args in [
+      "-d:useSysAssert -d:useGcAssert",
+      "-d:chronosStackTrace -d:chronosStrictException",
+      "-d:release",
+      "-d:release -d:chronosFutureTracking",
+    ]: run args, "tests/testall"
 
 task test_libbacktrace, "test with libbacktrace":
-  var commands = @[
-      commandStart & " -d:release --debugger:native -d:chronosStackTrace -d:nimStackTraceOverride --import:libbacktrace tests/",
+  var allArgs = @[
+      "-d:release --debugger:native -d:chronosStackTrace -d:nimStackTraceOverride --import:libbacktrace",
     ]
 
-  for testname in ["testall"]:
-    for cmd in commands:
-      let curcmd = cmd & testname
-      echo "\n" & curcmd
-      exec curcmd
-      rmFile "tests/" & testname
+  for args in allArgs:
+    run args, "tests/testall"