# GoCryptoTrader package Alert
[](https://github.com/thrasher-corp/gocryptotrader/actions/workflows/tests.yml)
[](https://github.com/thrasher-corp/gocryptotrader/blob/master/LICENSE)
[](https://godoc.org/github.com/thrasher-corp/gocryptotrader/exchanges/alert)
[](https://codecov.io/gh/thrasher-corp/gocryptotrader)
[](https://goreportcard.com/report/github.com/thrasher-corp/gocryptotrader)
This alert package is part of the GoCryptoTrader codebase.
## This is still in active development
You can track ideas, planned features and what's in progress on our [GoCryptoTrader Kanban board](https://github.com/orgs/thrasher-corp/projects/3).
Join our slack to discuss all things related to GoCryptoTrader! [GoCryptoTrader Slack](https://join.slack.com/t/gocryptotrader/shared_invite/zt-38z8abs3l-gH8AAOk8XND6DP5NfCiG_g)
## Alert
+ This package allows for multiple routines to wait for a state change on any required data.
### Examples:
+ Implementation:
```go
// SomeChangingType defines an example struct with an embedded alert.Notice
// type for easy access to the notice methods.
type SomeChangingType struct {
ValueThatChanges int64
alert.Notice
mu sync.Mutex // Protection for routine shenanigans
}
// Update will update in a separate routine
func (s *SomeChangingType) Update(newValue int64) {
// This simulates a changing variable or state
s.mu.Lock()
s.ValueThatChanges = newValue
// This will alert any routines that are currently waiting for a change
s.Alert()
s.mu.Unlock()
}
// WhatsTheValue will retrieve the value that was changed and should be
// different from the past value. Efficiency++
func (s *SomeChangingType) WhatsTheValue() int64 {
s.mu.Lock()
value := s.ValueThatChanges
s.mu.Unlock()
return value
}
```
+ Routine waiting for change:
```go
// ExampleRoutineThatWaits defines an exchange potential routine that will wait
// for an impending change.
func ExampleRoutineThatWaits(potentialChange *SomeChangingType) {
// Every iteration requires a Wait() call.
for range potentialChange.Wait(nil) {
val := potentialChange.WhatsTheValue()
fmt.Println("Value:", val)
}
}
// AnotherExampleRoutineThatWaits defines an exchange potential routine that
// will wait for an impending change.
func AnotherExampleRoutineThatWaits(potentialChange *SomeChangingType) {
// Every iteration requires a Wait() call.
for {
select {
case <-potentialChange.Wait(nil):
val := potentialChange.WhatsTheValue()
fmt.Println("Value:", val)
case <-shutdownChannel:
fmt.Println("Good-Bye!")
return
}
}
}
// WARNING: PLEASE DON'T DO THIS.
// This will stop alerting for this specific data type due to the shared nature
// of the underlying channels using a sync.Pool.
func ABadExampleRoutineThatWaits(potentialChange *SomeChangingType) {
capturedChannel := potentialChange.Wait(nil)
for {
select {
case <-capturedChannel:
// This will produce incorrect results or no change.
val := potentialChange.WhatsTheValue()
fmt.Println("Value:", val)
case <-shutdownChannel:
fmt.Println("Good-Bye!")
return
}
}
}
```
## Donations
If this framework helped you in any way, or you would like to support the developers working on it, please donate Bitcoin to:
***bc1qk0jareu4jytc0cfrhr5wgshsq8282awpavfahc***