Add new placeholder for latency in milliseconds

caddyhttp/httpserver/replacer.go

@@ -286,11 +286,22 @@ func (r *replacer) getSubstitution(key string) string {
 			return r.emptyValue
 		}
 		return roundDuration(time.Since(r.responseRecorder.start)).String()
+	case "{latency_ms}":
+		if r.responseRecorder == nil {
+			return r.emptyValue
+		}
+		elapsedDuration := time.Since(r.responseRecorder.start)
+		return strconv.FormatInt(convertToMilliseconds(elapsedDuration), 10)
 	}
 
 	return r.emptyValue
 }
 
+//convertToMilliseconds returns the number of milliseconds in the given duration
+func convertToMilliseconds(d time.Duration) int64 {
+	return d.Nanoseconds() / 1e6
+}
+
 // Set sets key to value in the r.customReplacements map.
 func (r *replacer) Set(key, value string) {
 	r.customReplacements["{"+key+"}"] = value

caddyhttp/httpserver/replacer_test.go

@@ -150,3 +150,21 @@ func TestRound(t *testing.T) {
 		}
 	}
 }
+
+func TestMillisecondConverstion(t *testing.T) {
+	var testCases = map[time.Duration]int64{
+		2 * time.Second:           2000,
+		9039492 * time.Nanosecond: 9,
+		1000 * time.Microsecond:   1,
+		127 * time.Nanosecond:     0,
+		0 * time.Millisecond:      0,
+		255 * time.Millisecond:    255,
+	}
+
+	for dur, expected := range testCases {
+		numMillisecond := convertToMilliseconds(dur)
+		if numMillisecond != expected {
+			t.Errorf("Expected %v. Got %v", expected, numMillisecond)
+		}
+	}
+}