flag: zero value for time.Duration not recognized

[xi2]

Please answer these questions before submitting your issue. Thanks!

1. What version of Go are you using (go version)?
   go version devel +4223294 Tue May 31 13:02:09 2016 +0000 linux/amd64

2. What operating system and processor architecture are you using (go env)?
   GOARCH="amd64"
   GOBIN=""
   GOEXE=""
   GOHOSTARCH="amd64"
   GOHOSTOS="linux"
   GOOS="linux"
   GOPATH="/home/user"
   GORACE=""
   GOROOT="/usr/lib/go"
   GOTOOLDIR="/usr/lib/go/pkg/tool/linux_amd64"
   CC="gcc"
   GOGCCFLAGS="-fPIC -m64 -pthread -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build043601680=/tmp/go-build -gno-record-gcc-switches"
   CXX="g++"
   CGO_ENABLED="1"

3. What did you do?
   Ran the following with argument -h:

   package main
   
   import "flag"
   
   func main() {
       _ = flag.Duration("duration", 0, "set a duration")
       flag.Parse()
   }

4. What did you expect to see?
   On Go 1.6 I see:

   Usage of test:
   -duration duration
         set a duration
   exit status 2
   

5. What did you see instead?

   Usage of test:
   -duration duration
         set a duration (default 0s)
   exit status 2
   

Does isZeroValue in flag/flags.go now need a case "0s":?

[mark-rushakoff]

The string version of a zero duration has been discussed before on the mailing list.

[gopherbot]

CL https://golang.org/cl/23581 mentions this issue.