cgo error

[fantajeon]

When I pass [] bytes variable to curl.Setopt with CURL_POSTFIELDS, I got error "cgo argument has go pointer to go pointer" at 268 line in easy.go:
panic(0x85ee60, 0xc8202200c0)
/usr/local/go/src/runtime/panic.go:464 +0x3e6
github.com/andelf/go-curl._cgoCheckPointer0(0x79f980, 0xc8202200a0, 0xc8202200b0, 0x1, 0x1, 0x7fc858001cc0)
??:0 +0x4d
github.com/andelf/go-curl.(*CURL).Setopt(0xc8201eb2c0, 0x271f, 0x78fb20, 0xc82020cca0, 0x0, 0x0)
/home/ubuntu/go/src/github.com/andelf/go-curl/easy.go:268 +0x2271

I changed the source file and tested as followings:
case []byte:
b := param.([]byte)
ptr := unsafe.Pointer(&b[0])
return newCurlError(C.curl_easy_setopt_string(p, C.CURLoption(opt), (*C.char)(ptr)))

How about my changed code.