Goroutine behaves differently on Windows and Linux - go

Question

I`m new to the GO. I have a following legacy code.
var db *sql.DB
func init() {
go feedChan()
connString := os.Getenv("DB_CONN")
var err error
db, err = sql.Open("postgres", connString)
if err != nil {
log.Fatalf("Failed to connect to database at %q: %q\n", connString, err)
}
// confirm connection
if err = db.Ping(); err != nil {
log.Fatalf("Unable to ping database at %q: %q\n", connString, err)
}
}
func feedChan() {
selectQuery, err := db.Prepare(`
SELECT id, proxy
FROM proxy
WHERE fail_count < 2
ORDER BY date_added DESC, last_used ASC, fail_count ASC
LIMIT 5
`)
....
Following code works on linux. But it fails on windows with nil error on
selectQuery, err := db.Prepare(`
Which make sense for me, since db initialized after a launch of feedChan goroutine. What doesnt make sense for me is why it work on linux.
So the question is why this code work at linux without errors?

Answer 1

That's probably a race condition. Import "time", put this line after go feedChan(), and see if it still works on Linux:
time.Sleep(3 * time.Second)
In order to avoid this situation, you could either initialize db before you spawn the routine (which uses db) or use some sort of barrier:
func init() {
barrier := make(chan int)
go feedChan(barrier)
connString := os.Getenv("DB_CONN")
var err error
db, err = sql.Open("postgres", connString)
if err != nil {
log.Fatalf("Failed to connect to database at %q: %q\n", connString, err)
// Retry.
} else {
barrier <- 1 // Opens barrier.
}
// ...
}
func feedChan(barrier chan int) {
<-barrier // Blocks until db is ready.
selectQuery, err := db.Prepare(`
SELECT id, proxy
FROM proxy
WHERE fail_count < 2
ORDER BY date_added DESC, last_used ASC, fail_count ASC
LIMIT 5
`)
// ...
}

Answer 2

After reading the first lines of your functions I just can say you that your legacy code has a huge bug and it can be easily fixed just moving this line go feedChan() to the end of the init() function.
Also note the main reason is not a race condition, just a matter of wait for the correct initialization of db variable.