Race Condition and Data Race

Data race is when one concurrent operation attempts to read a variable while at some undetermined time another concurrent operation is attempting to write to the same variable.

• occurs when two goroutines access the same variable concurrently and at least one of the accesses is a write

Data Race Condition

package main
import "fmt"

func main() {
   wait := make(chan struct{})
   n := 0
   go func() {
      n++ // read, increment, write
      close(wait)
   }()
   n++ // conflicting access
   <-wait
   fmt.Println(n) // Output: <unspecified>
}

Fix

func main() {
   ch := make(chan int)
   go func() {
      n := 0 // A local variable is only visible to one goroutine.
      n++
      ch <- n // The data leaves one goroutine...
   }()
   
   n := <-ch // ...and arrives safely in another.
   n++
   fmt.Println(n) // Output: 2
}

Race condition occurs when two or more operations must execute in the correct order, but the program has not been written so that this order is guaranteed to be maintained.

Race Confition

package main
import "fmt"

func deposit(balance *int, amount int){
    *balance += amount //add amount to balance
}

func withdraw(balance *int, amount int){
    *balance -= amount //subtract amount from balance
}

func main() {
    balance := 100 
    
    go deposit(&balance,10) //depositing 10

    withdraw(&balance, 50) //withdrawing 50

    fmt.Println(balance) 
}

=> Can use the Go race detector to detect potential issues.