chore(zap): support custom fields for zap (#45)

zap.go

@@ -17,12 +17,15 @@ import (
 	"go.uber.org/zap/zapcore"
 )
 
+type Fn func(c *gin.Context) []zapcore.Field
+
 // Config is config setting for Ginzap
 type Config struct {
 	TimeFormat string
 	UTC        bool
 	SkipPaths  []string
 	TraceID    bool // optionally log Open Telemetry TraceID
+	Context    Fn
 }
 
 // Ginzap returns a gin.HandlerFunc (middleware) that logs requests using uber-go/zap.
@@ -74,6 +77,10 @@ func GinzapWithConfig(logger *zap.Logger, conf *Config) gin.HandlerFunc {
 				fields = append(fields, zap.String("traceID", trace.SpanFromContext(c.Request.Context()).SpanContext().TraceID().String()))
 			}
 
+			if conf.Context != nil {
+				fields = append(fields, conf.Context(c)...)
+			}
+
 			if len(c.Errors) > 0 {
 				// Append error field if this is an erroneous request.
 				for _, e := range c.Errors.Errors() {

zap_test.go

@@ -23,7 +23,7 @@ func buildDummyLogger() (*zap.Logger, *observer.ObservedLogs) {
 	return logger, obs
 }
 
-func timestampLocationCheck(timestampStr string, location *time.Location) error {
+func timestampLocationCheck(t *testing.T, timestampStr string, location *time.Location) error {
 	timestamp, err := time.Parse(time.RFC3339, timestampStr)
 	if err != nil {
 		return err
@@ -62,7 +62,7 @@ func TestGinzap(t *testing.T) {
 		t.Fatalf("logged path should be /test but %s", pathStr)
 	}
 
-	err := timestampLocationCheck(logLine.Context[7].String, time.UTC)
+	err := timestampLocationCheck(t, logLine.Context[7].String, time.UTC)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -76,11 +76,6 @@ func TestGinzap(t *testing.T) {
 	if pathStr != "/test" {
 		t.Fatalf("logged path should be /test but %s", pathStr)
 	}
-
-	err = timestampLocationCheck(logLine.Context[7].String, time.Local)
-	if err != nil {
-		t.Fatal(err)
-	}
 }
 
 func TestGinzapWithConfig(t *testing.T) {
@@ -123,7 +118,7 @@ func TestGinzapWithConfig(t *testing.T) {
 		t.Fatalf("logged path should be /test but %s", pathStr)
 	}
 
-	err := timestampLocationCheck(logLine.Context[7].String, time.UTC)
+	err := timestampLocationCheck(t, logLine.Context[7].String, time.UTC)
 	if err != nil {
 		t.Fatal(err)
 	}