feat: add function to add Correlation IDs to logger

logging/correlation.go

@@ -48,3 +48,19 @@ func addCorrelationID(c *gin.Context, l *zap.SugaredLogger) {
 
 	c.Next()
 }
+
+// AddCorrelationIDToLogger takes correlation ID from the request context and
+// enriches the logger with them. The param logger cannot be nil.
+func AddCorrelationIDToLogger(c *gin.Context, l *zap.SugaredLogger) *zap.SugaredLogger {
+	if c == nil {
+		return l
+	}
+
+	// note: correlation IDs are in the request context, not in the gin context
+	ctx := c.Request.Context()
+
+	return l.With(
+		string(CorrelationIDName), ctx.Value(CorrelationIDName),
+		string(IntCorrelationIDName), ctx.Value(IntCorrelationIDName),
+	)
+}

logging/correlation_test.go

@@ -0,0 +1,55 @@
+package logging
+
+import (
+	"context"
+	"go.uber.org/zap/zaptest/observer"
+	"net/http"
+	"testing"
+
+	"github.com/gin-gonic/gin"
+	"github.com/stretchr/testify/assert"
+	"go.uber.org/zap"
+)
+
+func makeTestContext() *gin.Context {
+	c, _ := gin.CreateTestContext(nil)
+	ctx := context.WithValue(context.Background(), IntCorrelationIDName, "anything")
+	request, _ := http.NewRequestWithContext(ctx, http.MethodPost, "http://something", nil)
+	c.Request = request
+	return c
+}
+
+func Test_AddCorrelationIDToLogger_Nil_Context(t *testing.T) {
+	assert := assert.New(t)
+
+	base := zap.NewExample().Sugar()
+
+	assert.NotPanics(func() {
+		logger := AddCorrelationIDToLogger(nil, base)
+		assert.Equal(base, logger)
+	})
+}
+
+func Test_AddCorrelationIDToLogger_Nil_Logger(t *testing.T) {
+	assert := assert.New(t)
+
+	c := makeTestContext()
+
+	assert.Panics(func() {
+		AddCorrelationIDToLogger(c, nil)
+	})
+}
+
+func Test_AddCorrelationIDToLogger(t *testing.T) {
+	assert := assert.New(t)
+
+	c := makeTestContext()
+
+	observedZapCore, observedLogs := observer.New(zap.InfoLevel)
+	observedLogger := zap.New(observedZapCore)
+
+	logger := AddCorrelationIDToLogger(c, observedLogger.Sugar())
+	logger.Info("test")
+
+	assert.Equal("anything", observedLogs.All()[0].ContextMap()[string(IntCorrelationIDName)])
+}