Crash When Generating Services Using gogoproto.embed

[hunter001325]

1、I define protocolbuff message with gogoproto.embed, for example:
`
message UserBase {
optional int64 id = 1;
}

message UserDetail {
optional UserBase UserBase = 1 [(gogoproto.nullable) = false, (gogoproto.embed) = true];
optional string name = 2 [(gogoproto.nullable) = true];
}
`

crash as below:

There hasn't Names：

2、protocolbuff support embed filed：
https://godoc.org/github.com/gogo/protobuf/gogoproto#hdr-More_Canonical_Go_Structures

[zaquestion]

Making truss not panic should be pretty straightforward, but marshaling support may be limited.