diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
new file mode 100644
index 0000000..dab54a8
--- /dev/null
+++ b/.github/workflows/ci.yml
@@ -0,0 +1,26 @@
+name: CI
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+    branches: [main]
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        go-version: ['1.11', 'stable']
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: actions/setup-go@v5
+        with:
+          go-version: ${{ matrix.go-version }}
+
+      - name: Build
+        run: go build ./...
+
+      - name: Test
+        run: go test -race ./...
diff --git a/README.md b/README.md
index 6c82894..5636029 100644
--- a/README.md
+++ b/README.md
@@ -1 +1,8 @@
-# monotick
\ No newline at end of file
+# monotick
+
+Monotonic timestamps as int64 nanoseconds.
+
+[![Go Reference](https://pkg.go.dev/badge/github.com/dengaleev/monotick.svg)](https://pkg.go.dev/github.com/dengaleev/monotick)
+[![CI](https://github.com/dengaleev/monotick/actions/workflows/ci.yml/badge.svg)](https://github.com/dengaleev/monotick/actions/workflows/ci.yml)
+
+See [documentation](https://pkg.go.dev/github.com/dengaleev/monotick) for details.
diff --git a/go.mod b/go.mod
new file mode 100644
index 0000000..dde23de
--- /dev/null
+++ b/go.mod
@@ -0,0 +1,3 @@
+module github.com/dengaleev/monotick
+
+go 1.11
diff --git a/monotick.go b/monotick.go
new file mode 100644
index 0000000..2100430
--- /dev/null
+++ b/monotick.go
@@ -0,0 +1,40 @@
+// Package monotick provides monotonic timestamps as int64 nanoseconds.
+//
+// # Why int64?
+//
+// For measuring durations, you don't need wall clock time — just a counter.
+// int64 nanoseconds can represent ~292 years, while int32 overflows in ~2 seconds.
+//
+// # How it works
+//
+// A reference time.Time is captured at package init. Now() returns
+// time.Since(start) as int64 nanoseconds. This approach:
+//
+//   - Uses only public Go APIs (no go:linkname or runtime internals)
+//   - Requires no CGO
+//   - Works on all platforms
+//
+// Timestamps are relative to process start, not system boot. This is
+// sufficient for measuring durations within a process.
+//
+// # Example
+//
+//	start := monotick.Now()
+//	// ... do work ...
+//	elapsed := monotick.Since(start)
+package monotick
+
+import "time"
+
+var start = time.Now()
+
+// Now returns nanoseconds elapsed since process start (monotonic).
+func Now() int64 {
+	return int64(time.Since(start))
+}
+
+// Since returns nanoseconds elapsed since t, where t is a value
+// previously returned by Now.
+func Since(t int64) int64 {
+	return Now() - t
+}