Golang variable shadowing can mask race conditions

variable_shadowing_race.go

package main

import "time"

type cool struct{}

func (c *cool) add() error {
    return nil
}

func main() {
    c := &cool{}

    err := c.add()
    if err != nil {
        panic(err)
    }

    go func() {
        for i := 0; i < 6; i++ {
            err = c.add()
            if err != nil {
                panic(err)
            }
        }
    }()

    err = c.add()
    if err != nil {
        panic(err)
    }

    time.Sleep(4 * time.Second)
}

gofmt -s -w .; go run --race .

==================
WARNING: DATA RACE
Write at 0x00c0001120b0 by goroutine 6:
  main.main.func1()
      /tmp/cooler/main.go:21 +0x58

Previous write at 0x00c0001120b0 by main goroutine:
  main.main()
      /tmp/cooler/main.go:28 +0xf2

Goroutine 6 (running) created at:
  main.main()
      /tmp/cooler/main.go:19 +0xe4
==================

As you can see, the race has nothing to do with the add method. Rather, the err variable which is shadowed is now been written(assigned) to by different goroutines.

And go vet -all ./... does not catch it.
Neither does

gobin -u golang.org/x/tools/go/analysis/passes/shadow/cmd/shadow && \
go vet -vettool=$(which shadow) -strict ./...