main.go

func getDailyCost(dependency Dependency) (map[time.Time]float64, error) {
	currentTime := time.Now().Local()
	start := currentTime.AddDate(0, 0, -7).Format("2006-01-02")
	end := currentTime.Format("2006-01-02")

	layoutISO := "2006-01-02"

	datapoints := make(map[time.Time]float64, 0)

	filter := costexplorer.Expression{}

	if len(dependency.Name) != 0 {
		filter = costexplorer.Expression{
			And: []costexplorer.Expression{
				costexplorer.Expression{
					Dimensions: &costexplorer.DimensionValues{
						Key:    costexplorer.DimensionService,
						Values: []string{dependency.Service},
					},
				},
				costexplorer.Expression{
					Tags: &costexplorer.TagValues{
						Key:    aws.String(dependency.Tag),
						Values: []string{dependency.Name},
					},
				},
			},
		}
	} else {
		filter = costexplorer.Expression{
			Dimensions: &costexplorer.DimensionValues{
				Key:    costexplorer.DimensionService,
				Values: []string{dependency.Service},
			},
		}
	}

	req := svc.GetCostAndUsageRequest(&costexplorer.GetCostAndUsageInput{
		TimePeriod: &costexplorer.DateInterval{
			Start: &start,
			End:   &end,
		},
		Granularity: costexplorer.GranularityDaily,
		Metrics:     []string{"BlendedCost"},
		GroupBy: []costexplorer.GroupDefinition{
			costexplorer.GroupDefinition{
				Key:  aws.String("SERVICE"),
				Type: costexplorer.GroupDefinitionTypeDimension,
			},
		},
		Filter: &filter,
	})
	resp, err := req.Send(context.Background())
	if err != nil {
		return map[time.Time]float64{}, err
	}

	for _, period := range resp.ResultsByTime {
		t, _ := time.Parse(layoutISO, *period.TimePeriod.End)

		if len(period.Groups) == 0 {
			datapoints[t] = 0
		} else {
			value, _ := strconv.ParseFloat(*period.Groups[0].Metrics["BlendedCost"].Amount, 64)
			datapoints[t] = value
		}

	}

	return datapoints, nil
}