Only you can prevent race conditions.

blah.go

package blah

import (
	"sync/atomic"
)

var (
	n uint64
)

func UnsafeBlah() uint64 {
	n = n + 1
	return n
}

func SafeBlah() uint64 {
	return atomic.AddUint64(&n, 1)
}

blah_test.go

package blah

import "testing"

func BenchmarkUnsafeBlah(b *testing.B) {
	var u uint64
	b.RunParallel(func(pb *testing.PB) {
		for pb.Next() {
			u += UnsafeBlah()
		}
	})
	_ = u
}

func BenchmarkSafeBlah(b *testing.B) {
	var u uint64
	b.RunParallel(func(pb *testing.PB) {
		for pb.Next() {
			u += SafeBlah()
		}
	})
	_ = u
}

gistfile1.txt

go test -v -bench=. -race -cpu 1,2,4,8