I'm trying launch goroutines in an infinite loop until I get the response I'm looking for but the select is unreachable if I change for i := 0; i < 10; i++ {} to for {}. What's a pattern for solving this?
package main
import (
"fmt"
"math/rand"
"time"
)
func myFunc() float64 {
c := make(chan float64)
for i := 0; i < 10; i++ {
go func() {
var value float64
value = someOp()
if value > .9 {
c <- value
}
}()
}
// unreachable code the if the for loop above is infinite
for {
select {
case x := <-c:
return x
default:
}
}
}
func someOp() float64 {
rand.Seed(time.Now().UnixNano())
return rand.Float64()
}
func main() {
fmt.Println(myFunc())
}
Starting an unlimited number of goroutines is usually not a good idea. A better approach is to start a fixed number of goroutines that loop looking for an answer. Return from these goroutines when an answer is found.
func myFunc() float64 {
c := make(chan float64, 1) // Size 1 prevents race between main goroutine and workers
done := make(chan struct{})
defer close(done)
// Start a fixed number of goroutines
for i := 0; i < 10; i++ {
go func() {
for {
select {
case <-done:
// myfunc exited with result, return from this goroutine
return
default:
var value float64
value = someOp()
if value > .9 {
select {
case c <- value:
// This is first goroutine to send a value
default:
// Another goroutine sent a value
}
return
}
}
}
}()
}
return <-c
}