Not understanding race problems
Race problems can be among the hardest and most insidious bugs to fix.
Multiple goroutines data races
Mistake
i := 0
go func() {
i++
}()
go func() {
i++
}()
Fix
Using atomic operations
var i int64
go func() {
atomic.AddInt64(&i, 1)
}()
go func() {
atomic.AddInt64(&i, 1)
}()
Using mutexes
i := 0
mutex := sync.Mutex{}
go func() {
mutex.Lock()
i++
mutex.Unlock()
}()
go func() {
mutex.Lock()
i++
mutex.Unlock()
}()
Using channels
i := 0
ch := make(chan int)
go func() {
ch <- 1
}()
go func() {
ch <- 1
}()
i += <-ch
i += <-ch
Channel data races
Mistake
Synchronizing
i := 0
go func() {
i++ // Racer
}()
fmt.Println(i) // Racer
Buffered channels
i := 0
ch := make(chan struct{}, 1) // buffered
go func() {
i = 1
<-ch // A buffered receive happens before a send
}()
ch <- struct{}{}
fmt.Println(i)
Fix
Synchronizing
i := 0
ch := make(chan struct{})
go func() {
<-ch // this receive blocks until channel send
fmt.Println(i)
}()
i++
// alternatively we could close this channel for the same effect
ch <- struct{}{} // channel send
Buffered channels
i := 0
ch := make(chan struct{}) // unbuffered
go func() {
i = 1
<-ch
}()
ch <- struct{}{}
fmt.Println(i)