Please answer these questions before submitting your issue. Thanks!

1. What version of Go are you using (go version)?
   1.7
2. What operating system and processor architecture are you using (go env)?
   GOARCH="amd64"
   GOBIN=""
   GOEXE=""
   GOHOSTARCH="amd64"
   GOHOSTOS="darwin"
   GOOS="darwin"
   GOPATH="/Users/Zhengping/Documents/nsrg"
   GORACE=""
   GOROOT="/usr/local/go"
   GOTOOLDIR="/usr/local/go/pkg/tool/darwin_amd64"
   CC="clang"
   GOGCCFLAGS="-fPIC -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=/var/folders/c6/vwt_07cd62b102ynhmn2n7pm0000gn/T/go-build736045736=/tmp/go-build -gno-record-gcc-switches -fno-common"
   CXX="clang++"
   CGO_ENABLED="1"
3. What did you do?
   The x509 distributionPointName struct in x509.go is defined as

type distributionPointName struct {
FullName asn1.RawValue asn1:"optional,tag:0"
RelativeName pkix.RDNSequence asn1:"optional,tag:1"
}

But in RFC 5280, it is defined as

DistributionPointName ::= CHOICE {
fullName [0] GeneralNames,
nameRelativeToCRLIssuer [1] RelativeDistinguishedName }

Clearly DistributionPointName is a choice, FullName and RelativeName cannot be present at the same time. Please consider making the struct contain one asn1.RawValue element to fix this issue.

type distributionPointName struct {
Name asn1.RawValue
}