$ go version
go version devel +add507d4646f Tue Oct 08 13:13:40 2013 -0700 linux/amd64

What steps will reproduce the problem?
If possible, include a link to a program on play.golang.org.
1. Download will_crash.gz data file
2. Either download go_gunzip.go or take the program from
http://play.golang.org/p/lLS8o9c-RO
3. Run it
go go_gunzip.go < will_crash.gz

What is the expected output?
Before io.Copy
After io.Copy
<exit status 0>

What do you see instead?

$ go run go_gunzip.go < will_crash.gz 
2013/10/08 21:34:26 Before io.Copy
panic: runtime error: invalid memory address or nil pointer dereference
[signal 0xb code=0x1 addr=0x290 pc=0x424a53]

goroutine 1 [running]:
runtime.panic(0x4b3c60, 0x5b3328)
        /home/krasin/go/src/pkg/runtime/panic.c:266 +0xb6
compress/gzip.(*Reader).Read(0x0, 0xc210050000, 0x2000, 0x2000, 0x2005b6e58, ...)
        /home/krasin/go/src/pkg/compress/gzip/gunzip.go:200 +0x43
io/ioutil.devNull.ReadFrom(0x0, 0x7fd38de52180, 0x0, 0x0, 0x0, ...)
        /home/krasin/go/src/pkg/io/ioutil/ioutil.go:144 +0xb0
io.Copy(0x7fd38de51190, 0x0, 0x7fd38de52180, 0x0, 0x0, ...)
        /home/krasin/go/src/pkg/io/io.go:348 +0x124
main.main()
        /home/krasin/testdata/go_gunzip.go:20 +0x243
exit status 2

Which compiler are you using (5g, 6g, 8g, gccgo)?
6g

Which operating system are you using?
Ubuntu Linux 12.04 x86-64 (also tested on 13.04).

Which version are you using?  (run 'go version')

$ go version
go version devel +add507d4646f Tue Oct 08 13:13:40 2013 -0700 linux/amd64

Please provide any additional information below.

Attachments:

1. will_crash.gz (32768 bytes)
2. go_gunzip.go (359 bytes)