Go: Detect data races
Data races can happen easily and are hard to debug. Luckily, the Go runtime is often able to help.
Use -race
to enable the built-in data race detector.
$ go test -race somepkg
$ go run -race somepkg
Example
Here's a program with a data race:
package main
import "fmt"
func main() {
i := 0
go func() {
i++ // write
}()
fmt.Println(i) // concurrent read
}
Running this program with the -race
options tells us that there's a race between the write at line 7 and the read at line 9:
$ go run -race main.go
0
==================
WARNING: DATA RACE
Write by goroutine 6:
main.main.func1()
/tmp/main.go:7 +0x44
Previous read by main goroutine:
main.main()
/tmp/main.go:9 +0x7e
Goroutine 6 (running) created at:
main.main()
/tmp/main.go:8 +0x70
==================
Found 1 data race(s)
exit status 66
Details
The data race detector does not perform any static analysis. It checks the memory access in runtime and only for the code paths that are actually executed.
It runs on darwin/amd64, freebsd/amd64, linux/amd64 and windows/amd64.
The overhead varies, but typically there's a 5-10x increase in memory usage, and 2-20x increase in execution time.
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