implement correlationid middleware

.github/workflows/ci.yml

@@ -0,0 +1,33 @@
+name: build
+
+on:
+  push:
+    tags:
+      - v*
+    branches:
+      - master
+      - dev
+  pull_request:
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Setup Go environment
+        uses: actions/setup-go@v3.0.0
+        with:
+          go-version: 1.18
+
+      - name: checkout
+        uses: actions/checkout@v3.0.0
+
+      - name: build and test
+        run: |
+          go get -v
+          go test -timeout=60s
+          go build -race
+      
+      - name: Run golangci-lint
+        uses: golangci/golangci-lint-action@v3.1.0
+

correlation_id.go

@@ -0,0 +1,97 @@
+// Package correlationid provides handler for getting correlationid header from request or generate new and set it to request context.
+package correlationid
+
+import (
+	"context"
+	"fmt"
+	"net/http"
+
+	"github.com/google/uuid"
+)
+
+const (
+	// Header name. Can be overridden in Middlware struct.
+	DefaultHeaderName = "Correlation-Id"
+	// Key used for correlation id value in context.
+	ContextKey = "CorrelationId"
+)
+
+// Middlware struct with handler settings.
+type Middleware struct {
+	// Used for correlation id. Default "Correlation-Id".
+	HeaderName string
+	// Used for indicating should correlation id be included in response headers. Default "true".
+	IncludeInResponse bool
+	// Used for enforcing client include correlation id header in request. If "true" and header is absent - middlware will return BadRequest status code.
+	// Default "false".
+	EnforceHeader bool
+	// Used for correlation id generation if id is not included in request. By default uses github.com/google/uuid.
+	IdGenerator func() string
+}
+
+// Initialize default value of middleware. By default uses github.com/google/uuid for correlation id value.
+func New() Middleware {
+	return Middleware{
+		HeaderName:        DefaultHeaderName,
+		IncludeInResponse: true,
+		EnforceHeader:     false,
+		IdGenerator:       defaultGenerator,
+	}
+}
+
+// Handles http request and proceed correlation id based on Middlware settings.
+func (m *Middleware) Handle(next http.Handler) http.Handler {
+	return http.HandlerFunc(func(rw http.ResponseWriter, r *http.Request) {
+		headerName := m.getHeaderName()
+		corrId := r.Header.Get(headerName)
+		if corrId == "" {
+			if m.EnforceHeader {
+				http.Error(rw, fmt.Sprintf("%s header is required.", headerName), http.StatusBadRequest)
+				return
+			}
+
+			corrId = m.generateId()
+		}
+
+		if m.IncludeInResponse {
+			rw.Header().Set(headerName, corrId)
+		}
+
+		updCtx := WithCorrelationId(r.Context(), corrId)
+		next.ServeHTTP(rw, r.WithContext(updCtx))
+	})
+}
+
+// Returns correlation id from context if present. Otherwise "".
+func FromContext(ctx context.Context) string {
+	corrId, ok := ctx.Value(ContextKey).(string)
+	if ok {
+		return corrId
+	}
+	return ""
+}
+
+// Sets correlation id to context
+func WithCorrelationId(ctx context.Context, correlationId string) context.Context {
+	return context.WithValue(ctx, ContextKey, correlationId)
+}
+
+func defaultGenerator() string {
+	return uuid.NewString()
+}
+
+func (m *Middleware) getHeaderName() string {
+	if m.HeaderName == "" {
+		return DefaultHeaderName
+	}
+
+	return m.HeaderName
+}
+
+func (m *Middleware) generateId() string {
+	if m.IdGenerator != nil {
+		return m.IdGenerator()
+	}
+
+	return defaultGenerator()
+}