accesslog: add CSV format

relative to: https://github.com/kataras/iris/issues/1601

middleware/accesslog/csv_test.go

@@ -0,0 +1,54 @@
+package accesslog
+
+import (
+	"bytes"
+	"testing"
+	"time"
+
+	"github.com/kataras/iris/v12/core/memstore"
+)
+
+func TestCSV(t *testing.T) {
+	buf := new(bytes.Buffer)
+	ac := New(buf)
+	staticNow, _ := time.Parse(defaultTimeFormat, "1993-01-01 05:00:00")
+	ac.Clock = TClock(staticNow)
+	ac.SetFormatter(&CSV{
+		Header:       true,
+		LatencyRound: time.Second,
+		AutoFlush:    true,
+	})
+
+	lat, _ := time.ParseDuration("1s")
+
+	print := func() {
+		ac.Print(
+			nil,
+			lat,
+			"",
+			200,
+			"GET",
+			"/",
+			"::1",
+			"",
+			"Index",
+			573,
+			81,
+			nil,
+			[]memstore.StringEntry{{Key: "sleep", Value: "1s"}},
+			nil)
+	}
+
+	// print twice, the header should only be written once.
+	print()
+	print()
+
+	expected := `Timestamp,Latency,Code,Method,Path,IP,Req Values,In,Out,Request,Response
+725864400000,1s,200,GET,/,::1,sleep=1s,573,81,,Index
+725864400000,1s,200,GET,/,::1,sleep=1s,573,81,,Index
+`
+
+	if got := buf.String(); expected != got {
+		t.Fatalf("expected:\n%s\n\nbut got:\n%s", expected, got)
+	}
+}