diff --git a/.editorconfig b/.editorconfig
new file mode 100644
index 0000000..56a5c59
--- /dev/null
+++ b/.editorconfig
@@ -0,0 +1,19 @@
+# EditorConfig is awesome: https://EditorConfig.org
+
+# top-most EditorConfig file
+root = true
+
+# Unix-style newlines with a newline ending every file
+[*]
+end_of_line = lf
+insert_final_newline = true
+charset = utf-8
+indent_style = space
+indent_size = 2
+
+[{*.go,go.mod,Makefile}]
+indent_style = tab
+
+# Ignore paths
+[LICENSE]
+indent_size = unset
diff --git a/.github/workflows/go.yml b/.github/workflows/go.yml
new file mode 100644
index 0000000..4decab1
--- /dev/null
+++ b/.github/workflows/go.yml
@@ -0,0 +1,33 @@
+name: Go
+
+on:
+  push:
+    branches: [ 'main', 'release-*' ]
+  pull_request:
+    types: [opened, synchronize, reopened]
+
+jobs:
+
+  build:
+    name: Test
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        go-version:
+          - '1.18'
+    steps:
+
+      - name: Set up Go ${{ matrix.go-version }}
+        uses: actions/setup-go@v2
+        with:
+          go-version: ${{ matrix.go-version }}
+        id: go
+
+      - name: Check out code into the Go module directory
+        uses: actions/checkout@v2
+
+      - name: Test
+        run: go run gotest.tools/gotestsum@v1.8.0 --format testname --
+          -race -count=1 -short ./...
+        env:
+          FORCE_COLOR: true
diff --git a/.github/workflows/knative-style.yaml b/.github/workflows/knative-style.yaml
new file mode 100644
index 0000000..f34e11c
--- /dev/null
+++ b/.github/workflows/knative-style.yaml
@@ -0,0 +1,10 @@
+name: Code Style
+
+on:
+  pull_request:
+    branches: [ 'main', 'release-*' ]
+
+jobs:
+
+  style:
+    uses: knative/actions/.github/workflows/style.yaml@main
diff --git a/.golangci.yaml b/.golangci.yaml
new file mode 100644
index 0000000..4ad7c82
--- /dev/null
+++ b/.golangci.yaml
@@ -0,0 +1,36 @@
+run:
+  timeout: 5m
+  build-tags:
+    - e2e
+
+linters:
+  disable-all: false
+  presets:
+    - bugs
+    - unused
+    - complexity
+    - format
+    - performance
+    - style
+  enable:
+    - gci
+  disable:
+    - paralleltest
+    - nlreturn
+    - exhaustivestruct
+    - wsl
+    - godox
+    - scopelint
+    - maligned
+    - interfacer
+    - golint
+    - ireturn
+    - varnamelen
+    - gochecknoglobals
+
+issues:
+  exclude-rules:
+    - path: _test\.go
+      linters:
+        - wrapcheck
+
diff --git a/README.md b/README.md
index 899c750..119c2e4 100644
--- a/README.md
+++ b/README.md
@@ -1,2 +1,11 @@
-# go-retcode
-Deterministic process exit codes
+# retcode package for Go
+
+Deterministic process exit codes based on Go errors.
+
+## Usage
+
+```go
+err := fmt.Errorf("example error")
+os.Exit(retcode.Calc(err))
+```
+
diff --git a/go.mod b/go.mod
new file mode 100644
index 0000000..aa527f2
--- /dev/null
+++ b/go.mod
@@ -0,0 +1,3 @@
+module github.com/wavesoftware/go-retcode
+
+go 1.18
diff --git a/retcode.go b/retcode.go
new file mode 100644
index 0000000..0618282
--- /dev/null
+++ b/retcode.go
@@ -0,0 +1,21 @@
+package retcode
+
+import "hash/crc32"
+
+var (
+	// LowerBound is the lower bound of the POSIX retcode range. Use this to
+	// configure the package.
+	LowerBound = 1
+	// UpperBound is the upper bound of the POSIX retcode range. Use this to
+	// configure the package.
+	UpperBound = 255
+)
+
+// Calc will calculate an POSIX retcode from an error.
+func Calc(err error) int {
+	if err == nil {
+		return 0
+	}
+	upper := UpperBound - LowerBound
+	return int(crc32.ChecksumIEEE([]byte(err.Error())))%upper + LowerBound
+}
diff --git a/retcode_test.go b/retcode_test.go
new file mode 100644
index 0000000..3fb5526
--- /dev/null
+++ b/retcode_test.go
@@ -0,0 +1,44 @@
+package retcode_test
+
+import (
+	"fmt"
+	"testing"
+
+	"github.com/wavesoftware/go-retcode"
+)
+
+func TestCalc(t *testing.T) {
+	cases := testCases()
+	for i := range cases {
+		tt := cases[i]
+		t.Run(tt.name, func(t *testing.T) {
+			if got := retcode.Calc(tt.err); got != tt.want {
+				t.Errorf("Calc() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}
+
+func testCases() []testCase {
+	return []testCase{{
+		name: "nil",
+		err:  nil,
+		want: 0,
+	}, {
+		name: "errExample",
+		err:  errExample,
+		want: 133,
+	}, {
+		name: "error of wrap caused by 12345",
+		err:  fmt.Errorf("%w: 12345", errExample),
+		want: 249,
+	}}
+}
+
+var errExample = fmt.Errorf("example error")
+
+type testCase struct {
+	name string
+	err  error
+	want int
+}