Golang proposal: cmd/vet: report goroutine's leak using time.Ticker

Proposal Details

I propose the new rule about time.Ticker. Here is the example code.

package main

import (
    "fmt"
    "runtime"
    "time"
)

func main() {
    fmt.Println(runtime.NumGoroutine())
    t := Proc(time.Second)
    t.Stop()
    time.Sleep(5 * time.Second)
    fmt.Println(runtime.NumGoroutine())
}

func Proc(d time.Duration) *time.Ticker {
    t := time.NewTicker(d)
    go func() {
        for {
            select {
            case <-t.C:
                fmt.Println("tick")
            }
        }
    }()
    return t
}

This program must leak goroutine because it can't cancel the goroutine Proc generates. Ticker doesn't have the structure to cancel and I think primary Go developer may misread Stop is for canceling the Ticker.

Comment From: gabyhelp

Related Issues and Documentation

• time: document that time.Tick causes a resource leak #11662 (closed)
• time: stop time.Ticker when it is garbage collected #8001 (closed)
• proposal: time: Add TickerFunc #68482
• proposal: time: add a channel to time.Ticker to detect stopped tickers #35643 (closed)
• proposal: Go 2: time: deprecate time.Tick(d Duration) #37144 (closed)
• proposal: cmd/vet: report time.Tick and time.NewTicker scoped to select statements #48170 (closed)

_{(Emoji vote if this was helpful or unhelpful; more detailed feedback welcome in this discussion.)}

Comment From: seankhliao

For a check to be added to cmd/vet, we'd need evidence that the pattern it catches is common enough to be worth checking for, and has no false positives. I don't think this will meet that those requirements. I'd recommend starting with a third party linter, and we can reevaluate when we see sufficient adoption.