diff --git a/.github/dependabot.yml b/.github/dependabot.yml
new file mode 100644
index 0000000..e9c7a2e
--- /dev/null
+++ b/.github/dependabot.yml
@@ -0,0 +1,12 @@
+version: 2
+updates:
+  - package-ecosystem: gomod
+    directory: /
+    schedule:
+      interval: daily
+    open-pull-requests-limit: 10
+  - package-ecosystem: github-actions
+    directory: "/"
+    schedule:
+      interval: daily
+    open-pull-requests-limit: 10
diff --git a/.github/workflows/changelog.yml b/.github/workflows/changelog.yml
new file mode 100644
index 0000000..94b4efe
--- /dev/null
+++ b/.github/workflows/changelog.yml
@@ -0,0 +1,14 @@
+name: update changelog
+
+on:
+  release:
+    types: [released]
+
+permissions: {}
+
+jobs:
+  changelog:
+    permissions:
+      contents: write
+    secrets: inherit
+    uses: bavix/.github/.github/workflows/changelog.yml@0.3.3
diff --git a/.github/workflows/golangci-lint.yml b/.github/workflows/golangci-lint.yml
new file mode 100644
index 0000000..93676c9
--- /dev/null
+++ b/.github/workflows/golangci-lint.yml
@@ -0,0 +1,26 @@
+name: golangci-lint
+on:
+  push:
+    branches:
+      - master
+  pull_request:
+permissions:
+  contents: read
+jobs:
+  golangci:
+    name: lint
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        go-version: [ '1.25' ]
+    steps:
+      - uses: actions/checkout@v5
+      - name: Setup Go
+        uses: actions/setup-go@v5
+        with:
+          go-version: ${{ matrix.go-version }}
+          cache: true
+      - name: golangci-lint
+        uses: golangci/golangci-lint-action@v8
+        with:
+          version: v2.3.0
diff --git a/.github/workflows/semgrep.yml b/.github/workflows/semgrep.yml
new file mode 100644
index 0000000..e559dff
--- /dev/null
+++ b/.github/workflows/semgrep.yml
@@ -0,0 +1,8 @@
+name: semgrep
+
+on:
+  pull_request:
+
+jobs:
+  semgrep:
+    uses: bavix/.github/.github/workflows/go-semgrep.yml@0.3.3
diff --git a/.github/workflows/unit.yml b/.github/workflows/unit.yml
new file mode 100644
index 0000000..eeb2897
--- /dev/null
+++ b/.github/workflows/unit.yml
@@ -0,0 +1,26 @@
+name: Unit
+on:
+  pull_request:
+    branches:
+      - master
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        go-version: [ '1.24', '1.25' ]
+    steps:
+      - uses: actions/checkout@v5
+      - name: Setup Go
+        uses: actions/setup-go@v5
+        with:
+          go-version: ${{ matrix.go-version }}
+          cache: true
+      - name: Test with Go
+        run: go test ./...
+      - name: Upload Go test results
+        uses: actions/upload-artifact@v4
+        with:
+          name: Go-results-${{ matrix.go-version }}
+          path: TestResults-${{ matrix.go-version }}.json
diff --git a/.golangci.yml b/.golangci.yml
new file mode 100644
index 0000000..146d688
--- /dev/null
+++ b/.golangci.yml
@@ -0,0 +1,35 @@
+version: "2"
+linters:
+  default: all
+  disable:
+    - wsl
+    - wrapcheck
+    - revive
+  settings:
+    depguard:
+      rules:
+        main:
+          allow:
+            - $gostd
+            - github.com
+            - golang.org
+            - google.golang.org
+    lll:
+      line-length: 140
+    wsl_v5:
+      allow-first-in-block: true
+      allow-whole-block: false
+      branch-max-lines: 2
+
+formatters:
+  enable:
+    - gci
+    - gofmt
+    - gofumpt
+    - goimports
+  settings:
+    gci:
+      sections:
+        - Standard
+        - Default
+        - Prefix(github.com/gripmock)
diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..ff8918f
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,10 @@
+.PHONY: *
+
+test:
+	go test -tags mock -race -cover ./...
+
+lint:
+	go run github.com/golangci/golangci-lint/v2/cmd/golangci-lint@v2.3.0 run --color always ${args}
+
+lint-fix:
+	make lint args=--fix
\ No newline at end of file
diff --git a/README.md b/README.md
index 2b40412..eeb50b8 100644
--- a/README.md
+++ b/README.md
@@ -1 +1,77 @@
-# types
\ No newline at end of file
+# Gripmock Types
+
+A package of custom types for [Gripmock](https://github.com/bavix/gripmock) that solves JSON serialization/deserialization problems.
+
+## Problem
+
+In [issue #648](https://github.com/bavix/gripmock/issues/648), a problem was identified with deserializing string time values into `time.Duration`. When trying to use JSON like:
+
+```json
+{
+  "output": {
+    "delay": "100ms"
+  }
+}
+```
+
+The following error occurred:
+```
+json: cannot unmarshal number { into Go struct field Output.Delay of type time.Duration
+```
+
+## Solution
+
+The `types` package provides a custom `Duration` type that correctly handles string time values in JSON.
+
+## Available Types
+
+### Duration
+
+A custom type alias for `time.Duration` that provides JSON marshaling/unmarshaling support for string values.
+
+#### Supported formats
+
+Only string values are supported:
+```json
+{
+  "delay": "100ms"
+}
+```
+
+Valid duration formats:
+- `"100ms"` - milliseconds
+- `"2s"` - seconds  
+- `"1m"` - minutes
+- `"1h"` - hours
+- `"1h30m"` - combined formats
+
+#### Usage
+
+```go
+type Output struct {
+    Delay types.Duration `json:"delay"`
+    Data  map[string]interface{} `json:"data"`
+}
+
+var output Output
+json.Unmarshal([]byte(`{"delay": "100ms"}`), &output)
+
+// Access the duration value
+duration := time.Duration(output.Delay)
+```
+
+## Installation
+
+```bash
+go get github.com/gripmock/types
+```
+
+## Testing
+
+```bash
+go test ./...
+```
+
+## License
+
+MIT License - see [LICENSE](LICENSE) file.
\ No newline at end of file
diff --git a/duration.go b/duration.go
new file mode 100644
index 0000000..eb4afa5
--- /dev/null
+++ b/duration.go
@@ -0,0 +1,36 @@
+// Package types provides custom JSON types for Gripmock.
+package types
+
+import (
+	"encoding/json"
+	"time"
+)
+
+// Duration is a custom type alias for time.Duration that provides
+// JSON marshaling/unmarshaling support for string values like "100ms".
+type Duration time.Duration
+
+// UnmarshalJSON implements json.Unmarshaler interface.
+func (d *Duration) UnmarshalJSON(data []byte) error {
+	// Try to unmarshal as string first
+	var s string
+
+	err := json.Unmarshal(data, &s)
+	if err == nil {
+		duration, err := time.ParseDuration(s)
+		if err != nil {
+			return err
+		}
+
+		*d = Duration(duration)
+
+		return nil
+	}
+
+	return json.Unmarshal(data, (*time.Duration)(d))
+}
+
+// MarshalJSON implements json.Marshaler interface.
+func (d Duration) MarshalJSON() ([]byte, error) {
+	return json.Marshal(time.Duration(d).String())
+}
diff --git a/duration_test.go b/duration_test.go
new file mode 100644
index 0000000..4372bad
--- /dev/null
+++ b/duration_test.go
@@ -0,0 +1,78 @@
+package types_test
+
+import (
+	"encoding/json"
+	"testing"
+	"time"
+
+	"github.com/gripmock/types"
+)
+
+func TestDuration_UnmarshalJSON(t *testing.T) {
+	t.Parallel()
+
+	tests := []struct {
+		name    string
+		input   string
+		want    time.Duration
+		wantErr bool
+	}{
+		{
+			name:    "string with ms",
+			input:   `"100ms"`,
+			want:    100 * time.Millisecond,
+			wantErr: false,
+		},
+		{
+			name:    "string with seconds",
+			input:   `"2s"`,
+			want:    2 * time.Second,
+			wantErr: false,
+		},
+		{
+			name:    "invalid duration string",
+			input:   `"invalid"`,
+			want:    0,
+			wantErr: true,
+		},
+	}
+
+	for _, testCase := range tests {
+		// Go 1.22+ runs subtests in parallel safely without copying loop var.
+		t.Run(testCase.name, func(t *testing.T) {
+			t.Parallel()
+
+			var duration types.Duration
+
+			err := json.Unmarshal([]byte(testCase.input), &duration)
+
+			if (err != nil) != testCase.wantErr {
+				t.Errorf("Duration.UnmarshalJSON() error = %v, wantErr %v", err, testCase.wantErr)
+
+				return
+			}
+
+			if !testCase.wantErr && time.Duration(duration) != testCase.want {
+				t.Errorf("Duration.UnmarshalJSON() = %v, want %v", time.Duration(duration), testCase.want)
+			}
+		})
+	}
+}
+
+func TestDuration_MarshalJSON(t *testing.T) {
+	t.Parallel()
+
+	duration := types.Duration(100 * time.Millisecond)
+	expected := `"100ms"`
+
+	got, err := json.Marshal(duration)
+	if err != nil {
+		t.Errorf("Duration.MarshalJSON() error = %v", err)
+
+		return
+	}
+
+	if string(got) != expected {
+		t.Errorf("Duration.MarshalJSON() = %v, want %v", string(got), expected)
+	}
+}
diff --git a/go.mod b/go.mod
new file mode 100644
index 0000000..f9a5026
--- /dev/null
+++ b/go.mod
@@ -0,0 +1,3 @@
+module github.com/gripmock/types
+
+go 1.24