WUMUXIAN/aws-slack-bot: jobs/slack_job.go; 50 LoC

Found a possible issue in [WUMUXIAN/aws-slack-bot](https://www.github.com/WUMUXIAN/aws-slack-bot) at [jobs/slack_job.go](https://github.com/WUMUXIAN/aws-slack-bot/blob/fc939245211eb85a42cd4ea81744c5fa4f820333/jobs/slack_job.go#L85-L134)

Below is the message reported by the analyzer for this snippet of code. Beware that the analyzer only reports the first issue it finds, so please do not limit your consideration to the contents of the below message.

> range-loop variable usage used in defer or goroutine at line 87

[Click here to see the code in its original context.](https://github.com/WUMUXIAN/aws-slack-bot/blob/fc939245211eb85a42cd4ea81744c5fa4f820333/jobs/slack_job.go#L85-L134)

Click here to show the 50 line(s) of Go which triggered the analyzer.

```go
for region, usage := range o.regionUsage {
go func() {
usage.ec2UsageChan <- stats.GetEC2Usage(usage.Sess)
}()

now := time.Now().UTC()
currentYear, currentMonth, _ := now.Date()
currentLocation := now.Location()
firstDayOfMonth := time.Date(currentYear, currentMonth, 1, 0, 0, 0, 0, currentLocation)
lastDayOfMonth := firstDayOfMonth.AddDate(0, 1, 0).Add(-time.Second)
go func() {
usage.s3UsageChan <- stats.GetS3Usage(usage.Sess, firstDayOfMonth, lastDayOfMonth)
}()
go func() {
usage.cloudFrontUsageChan <- stats.GetCloudFrontUsage(usage.Sess, firstDayOfMonth, lastDayOfMonth)
}()
go func() {
usage.rdsUsageChan <- stats.GetRDSUsage(usage.Sess, firstDayOfMonth, lastDayOfMonth)
}()
go func() {
usage.elasticacheUsageChan <- stats.GetElasticacheUsage(usage.Sess, firstDayOfMonth, lastDayOfMonth)
}()
go func() {
// fmt.Println("Gather accumulated estimated billing for this month", firstDayOfMonth, lastDayOfMonth)
month, average := stats.GetEstimatedBilling(usage.Sess, firstDayOfMonth, lastDayOfMonth)
usage.billingEstimationCurrentMonthChan <- []float64{month, average}
}()

firstDayOfLastMonth := firstDayOfMonth.AddDate(0, -1, 0)
lastDayOfLastMonth := firstDayOfLastMonth.AddDate(0, 1, 0).Add(-time.Second)
go func() {
// fmt.Println("Gather accumulated estimated billing for last month", firstDayOfLastMonth, lastDayOfLastMonth)
month, average := stats.GetEstimatedBilling(usage.Sess, firstDayOfLastMonth, lastDayOfLastMonth)
usage.billingEstimationLastMonthChan <- []float64{month, average}
}()

ec2UsageMap[region] = <-usage.ec2UsageChan
s3UsageMap[region] = <-usage.s3UsageChan
cloudFrontUsageMap[region] = <-usage.cloudFrontUsageChan
rdsUsageMap[region] = <-usage.rdsUsageChan
elasticacheUsageMap[region] = <-usage.elasticacheUsageChan

billingEstimation := <-usage.billingEstimationCurrentMonthChan
billingEstimationCurrentMonth[0] += billingEstimation[0]
billingEstimationCurrentMonth[1] += billingEstimation[1]

billingEstimation = <-usage.billingEstimationLastMonthChan
billingEstimationLastMonth[0] += billingEstimation[0]
billingEstimationLastMonth[1] += billingEstimation[1]
}

```

Leave a reaction on this issue to contribute to the project by classifying this instance as a **Bug** :-1:, **Mitigated** :+1:, or **Desirable Behavior** :rocket:
See the descriptions of the classifications [here](https://github.com/github-vet/rangeclosure-findings#how-can-i-help) for more information.

commit ID: fc939245211eb85a42cd4ea81744c5fa4f820333