http://go-tour-jp.appspot.com/#70

gistfile1.go

package main

import (
    "fmt"
    "code.google.com/p/go-tour/tree"
)

// Walk walks the tree t sending all values
// from the tree to the channel ch.
func Walk(t *tree.Tree, ch chan int) {
    Walk(t.Left, ch)
    ch <- t.Value
    Walk(t.Right, ch)
}

// Same determines whether the trees
// t1 and t2 contain the same values.
func Same(t1, t2 *tree.Tree) bool {
    ch1 := make(chan int, 100)
    ch2 := make(chan int, 100)
  	go Walk(t1, ch1)
  	go Walk(t2, ch2)
   
    for <- ch1 == <- ch2 {
    }
    
    return false
}

func main() {
    if Same(tree.New(1), tree.New(1)) {
    	fmt.Println("yay")
    }else {
    	fmt.Println("oh...")
    }
}

gistfile2.txt

panic: runtime error: invalid memory address or nil pointer dereference
[signal 0xb code=0xffffffff addr=0x0 pc=0x2002e]

goroutine 3 [running]:
runtime.panic(0xefc20, 0x1b6244)
	/tmp/sandbox/go/src/pkg/runtime/panic.c:266 +0xe0
runtime.panicstring(0x1b6244, 0x0)
	/tmp/sandbox/go/src/pkg/runtime/panic.c:489 +0x120
runtime.sigpanic()
	/tmp/sandbox/go/src/pkg/runtime/os_nacl.c:254 +0x80
main.Walk(0x0, 0x1054b540)
	/tmpfs/gosandbox-27483c41_bba89adc_7ac47c0a_3326acef_21b77f1d/prog.go:11 +0x2e
main.Walk(0x1052f160, 0x1054b540)
	/tmpfs/gosandbox-27483c41_bba89adc_7ac47c0a_3326acef_21b77f1d/prog.go:11 +0x60
main.Walk(0x1052f130, 0x1054b540)
	/tmpfs/gosandbox-27483c41_bba89adc_7ac47c0a_3326acef_21b77f1d/prog.go:11 +0x60
main.Walk(0x1052f120, 0x1054b540)
	/tmpfs/gosandbox-27483c41_bba89adc_7ac47c0a_3326acef_21b77f1d/prog.go:11 +0x60
main.Walk(0x1052f110, 0x1054b540)
	/tmpfs/gosandbox-27483c41_bba89adc_7ac47c0a_3326acef_21b77f1d/prog.go:11 +0x60
runtime.goexit()
	/tmp/sandbox/go/src/pkg/runtime/proc.c:1394
created by main.Same
	/tmpfs/gosandbox-27483c41_bba89adc_7ac47c0a_3326acef_21b77f1d/prog.go:21 +0xa0

goroutine 1 [chan receive]:
runtime.park(0x23460, 0x1054b56c, 0x1b6694, 0x10501790)
	/tmp/sandbox/go/src/pkg/runtime/proc.c:1342 +0x80
runtime.chanrecv(0xd9ec0, 0x1054b540, 0xfeee1f08, 0x0, 0x0, ...)
	/tmp/sandbox/go/src/pkg/runtime/chan.goc:305 +0x2c0
runtime.chanrecv1(0xd9ec0, 0x1054b540, 0x64, 0x0)
	/tmp/sandbox/go/src/pkg/runtime/chan.goc:360 +0x40
main.Same(0x1052f110, 0x1052f1b0, 0x1052f1b0, 0x6980)
	/tmpfs/gosandbox-27483c41_bba89adc_7ac47c0a_3326acef_21b77f1d/prog.go:24 +0x100
main.main()
	/tmpfs/gosandbox-27483c41_bba89adc_7ac47c0a_3326acef_21b77f1d/prog.go:31 +0x80
runtime.main()
	/tmp/sandbox/go/src/pkg/runtime/proc.c:220 +0x1c0
runtime.goexit()
	/tmp/sandbox/go/src/pkg/runtime/proc.c:1394

goroutine 2 [syscall]:
runtime.notetsleepg(0xfeefdf88, 0x0, 0xf8475800, 0xd)
	/tmp/sandbox/go/src/pkg/runtime/lock_sema.c:254 +0xa0
runtime.MHeap_Scavenger()
	/tmp/sandbox/go/src/pkg/runtime/mheap.c:463 +0xc0
runtime.goexit()
	/tmp/sandbox/go/src/pkg/runtime/proc.c:1394
created by runtime.main
	/tmp/sandbox/go/src/pkg/runtime/proc.c:179

goroutine 4 [runnable]:
main.Walk(0x1052f1b0, 0x1054b700)
	/tmpfs/gosandbox-27483c41_bba89adc_7ac47c0a_3326acef_21b77f1d/prog.go:10
runtime.goexit()
	/tmp/sandbox/go/src/pkg/runtime/proc.c:1394
created by main.Same
	/tmpfs/gosandbox-27483c41_bba89adc_7ac47c0a_3326acef_21b77f1d/prog.go:22 +0xe0
 [process exited with non-zero status]

Program exited.

goの参照はnilの可能性がある. if t.Left != nilとかする